Every industry has its jargon, but SEO seems to have more than most. Crawl budget. Canonical URLs. E-E-A-T. Core Web Vitals. If you've ever sat through a meeting with an agency or skimmed an SEO report and quietly wondered what half the words meant, you're in the right place. This SEO glossary explains more than 50 of the most important SEO terms in plain English — no acronyms left undefined, no assumptions about what you already know. Bookmark this page, and the next time a piece of SEO terminology stumps you, the answer is one search away. And if you want the bigger picture first, start with our beginner's guide on what SEO is and how it works, then come back here whenever a term needs decoding.
Search Engine Basics
These are the foundational terms behind everything you need to know about SEO. If you understand how a search engine discovers, stores, and orders web pages, every other definition in this glossary will make more sense.
Search Engine
A search engine is software that helps people find information on the internet — Google, Bing, and DuckDuckGo are the best-known examples. It works by scanning billions of web pages, storing what it finds, and serving up the most relevant results when someone types a query.
SERP (Search Engine Results Page)
The SERP is the page you see after typing a search into Google. It contains organic listings, paid ads, and increasingly rich features like maps, images, "People Also Ask" boxes, and AI-generated overviews. SEO is essentially the practice of winning better real estate on the SERP.
Organic Results
Organic results are the unpaid listings on a search results page, ranked purely on merit as judged by the search engine's algorithm. You can't buy your way into them — you earn your position through relevant, high-quality content and a trustworthy website.
Paid Results (PPC)
Paid results are advertisements that appear on the SERP, usually marked "Sponsored." Advertisers pay per click (PPC) through platforms like Google Ads. Paid results stop the moment the budget runs out, while organic rankings keep working for free.
Crawling
Crawling is how search engines discover content: automated programs follow links from page to page across the web, reading everything they find. If a page can't be crawled, it can't rank. Our guide on how search engines work walks through this process step by step.
Googlebot
Googlebot is the name of Google's web crawler — the program that visits and reads web pages so they can be added to Google's index. When people talk about "the spider" or "the bot" visiting your site, this is usually what they mean.
Indexing
Indexing is what happens after crawling: the search engine analyzes a page's content and stores it in a giant database called the index. Only indexed pages are eligible to appear in search results, which is why "Why isn't my page indexed?" is one of the most common SEO questions.
Ranking
Ranking is the process of ordering indexed pages from most to least relevant for a given search query. Search engines weigh hundreds of signals — content quality, authority, speed, mobile-friendliness — to decide which page deserves position one.
Algorithm
The algorithm is the complex system of rules and machine-learning models a search engine uses to rank pages. Google updates its algorithm thousands of times a year, including major "core updates" that can visibly shift rankings across the web.
Algorithm Update
An algorithm update is a change Google makes to how it evaluates and ranks pages. Most are tiny, but named core updates can cause significant traffic gains or losses overnight. Google documents confirmed updates in its Search Central update history.
Keyword Terms
Keywords are where every SEO campaign begins. These definitions cover the vocabulary you'll meet in any keyword tool or content brief — and our keyword research guide for beginners shows you how to put them into practice.
Keyword
A keyword is any word or phrase people type into a search engine — from a single word like "plumber" to a full question like "how much does a website cost." In SEO, keywords are the targets you optimize pages around.
Seed Keyword
A seed keyword is the broad starting term you feed into a research tool to generate hundreds of related keyword ideas. "Digital marketing" is a seed keyword; "digital marketing agency for dentists in Denver" is one of the many specific phrases it can lead you to.
Search Volume
Search volume is the average number of times a keyword is searched per month. High volume means a bigger potential audience, but it usually comes with more competition — which is why volume should never be evaluated in isolation.
Keyword Difficulty
Keyword difficulty is a score (usually 0–100) that estimates how hard it will be to rank on page one for a keyword, based mainly on the strength of the sites already ranking. New websites generally get faster wins by targeting low-difficulty keywords first.
Long-Tail Keyword
A long-tail keyword is a longer, more specific phrase with lower search volume but clearer intent — "best running shoes for flat feet women" rather than "shoes." Long-tail keywords are easier to rank for and typically convert better because the searcher knows exactly what they want.
Search Intent
Search intent is the reason behind a search: to learn something (informational), find a specific site (navigational), compare options (commercial), or buy (transactional). Matching your content to intent is arguably the single most important ranking consideration in modern SEO.
LSI / Related Terms
Related terms (often loosely called "LSI keywords") are words and phrases semantically connected to your main topic — for a page about coffee, terms like "espresso," "roast," and "caffeine." Using them naturally helps search engines understand your page's full context.
Keyword Cannibalization
Keyword cannibalization happens when multiple pages on your site compete for the same keyword, splitting authority and confusing search engines about which page to rank. The fix is usually to merge the pages or clearly differentiate their targets.
On-Page SEO Terms
On-page SEO covers everything you control directly within a web page. For the full hands-on walkthrough of these elements, see our complete on-page SEO guide.
Title Tag
The title tag is the HTML title of a page — the clickable blue headline in search results and the label on the browser tab. It's one of the strongest on-page signals, so it should include your target keyword and give people a compelling reason to click.
Meta Description
The meta description is the short summary that appears under your title in search results. It doesn't directly influence rankings, but a persuasive one lifts your click-through rate — which means more traffic from the same position.
H1 Tag
The H1 is the main on-page headline, and each page should have exactly one. It tells both visitors and search engines what the page is about, and it usually mirrors (but doesn't have to match) the title tag.
Header Tags (H2–H6)
Header tags structure your content into sections and subsections, like chapters in a book. Clear headings make long pages scannable for readers and help search engines understand your content hierarchy — they're also where featured snippets often come from.
Alt Text
Alt text is a written description of an image embedded in the HTML. It helps visually impaired users who rely on screen readers, gives search engines context they can't "see," and displays when an image fails to load.
Internal Link
An internal link connects one page on your website to another page on the same site. Internal links help visitors navigate, spread authority between pages, and show search engines which content matters most — every link in this glossary to another Jupiter guide is an internal link in action.
External Link
An external link points from your site to a different website. Linking out to credible sources signals well-researched content; earning external links pointing back at you (backlinks) is a different — and far more valuable — matter covered below.
Canonical URL
A canonical URL is the "official" version of a page you declare when similar or duplicate versions exist (for example, with and without tracking parameters). It tells search engines which URL should receive the ranking credit.
Duplicate Content
Duplicate content is identical or near-identical content appearing at more than one URL, on your site or across sites. It rarely triggers a penalty, but it dilutes ranking signals and can cause the wrong version of a page to rank.
Thin Content
Thin content is a page that offers little or no real value — a few generic sentences, doorway pages, or auto-generated text. Search engines actively filter thin pages out of results, so every page you publish should justify its existence.
Keyword Stuffing
Keyword stuffing is the outdated tactic of cramming a keyword into a page unnaturally often in the hope of ranking higher. Modern algorithms treat it as spam; write for humans and let keywords appear where they fit naturally.
Technical SEO Terms
Technical SEO makes sure search engines can access, understand, and trust your site's infrastructure. Our technical SEO audit checklist shows you how to check every one of these items on your own site.
Technical SEO
Technical SEO is the practice of optimizing your website's infrastructure — speed, security, crawlability, mobile experience — so search engines can work with it efficiently. It's the foundation layer: great content on a technically broken site is invisible content.
Core Web Vitals
Core Web Vitals are Google's three user-experience metrics: how fast your main content loads (LCP), how quickly the page responds to interaction (INP), and how visually stable it is while loading (CLS). They're a confirmed ranking factor, measurable with Google's free PageSpeed Insights tool.
Page Speed
Page speed is how quickly your page loads and becomes usable. Faster pages rank better, keep more visitors, and convert more of them — every extra second of load time measurably increases the share of people who give up and leave.
Crawl Budget
Crawl budget is the amount of attention a search engine is willing to spend crawling your site in a given period. Small sites rarely need to worry about it, but large sites with thousands of pages must avoid wasting crawls on duplicates, redirects, and junk URLs.
Robots.txt
Robots.txt is a small text file at the root of your website that tells crawlers which areas they may and may not visit. It's powerful and dangerous in equal measure — one wrong line can accidentally block your entire site from Google.
XML Sitemap
An XML sitemap is a machine-readable file listing all the pages you want search engines to find and index. Think of it as handing the crawler a map of your site instead of hoping it discovers every page by following links.
Schema Markup
Schema markup is structured data code added to a page that spells out exactly what the content is — a recipe, a review, an event, a local business. It can earn you rich results like star ratings and FAQ dropdowns in the SERP; our schema markup guide explains how to implement it.
HTTPS / SSL
HTTPS is the secure version of the web's transfer protocol, enabled by an SSL/TLS certificate that encrypts data between the visitor and your server. It's been a Google ranking signal since 2014, and browsers flag non-HTTPS sites as "Not Secure."
Mobile-First Indexing
Mobile-first indexing means Google ranks your site based on its mobile version, not the desktop one. If content or links are missing on mobile, they effectively don't exist for ranking purposes — see our mobile SEO best practices for how to get this right.
Redirect (301 / 302)
A redirect automatically forwards visitors and search engines from one URL to another. A 301 is permanent and passes ranking authority to the new URL; a 302 is temporary and tells search engines the original page will return.
404 Error
A 404 is the "page not found" error a server returns when a URL doesn't exist. A few 404s are normal, but broken links to important pages waste crawl budget, lose backlink value, and frustrate visitors — fix them with 301 redirects to the most relevant live page.
Off-Page & Authority Terms
Off-page SEO is about reputation: what the rest of the internet says about your site. These are the terms you'll hear whenever authority and trust come up.
Backlink
A backlink is a link from another website to yours. Search engines treat backlinks like votes of confidence — the more high-quality sites that link to you, the more trustworthy you appear. Our guide on how to build backlinks covers the tactics that actually work.
Referring Domain
A referring domain is a unique website that links to you, regardless of how many individual links it sends. Fifty backlinks from fifty different domains are far more valuable than fifty links from a single site.
Anchor Text
Anchor text is the visible, clickable text of a link. It gives search engines a hint about the linked page's topic — which is why descriptive anchors like "keyword research guide" beat generic ones like "click here."
Domain Authority
Domain authority is a third-party score (Moz's Domain Authority, Ahrefs' Domain Rating) that predicts how well a site can rank based largely on its backlink profile. Google doesn't use these exact scores, but they're useful shorthand for comparing site strength.
Nofollow
A nofollow attribute tells search engines not to pass ranking credit through a link. Links from comments, forums, and most social platforms are nofollow by default — they can still send traffic, but they carry little direct SEO weight.
Dofollow
"Dofollow" is the informal name for a normal link with no nofollow attribute — the default state of any link. These are the links that pass authority (often called "link equity" or "link juice") from one site to another.
Link Building
Link building is the deliberate practice of earning backlinks through outreach, digital PR, guest posting, and creating content people naturally want to cite. Done well, it's the most powerful lever for growing authority; done badly (buying spammy links), it can trigger penalties.
E-E-A-T
E-E-A-T stands for Experience, Expertise, Authoritativeness, and Trustworthiness — the framework from Google's quality guidelines that describes what credible content looks like. It matters most for health, finance, and other high-stakes topics; our E-E-A-T guide explains how to demonstrate it on your site.
White Hat vs. Black Hat SEO
White hat SEO follows search engine guidelines: helpful content, honest links, good user experience. Black hat SEO tries to game the algorithm with cloaking, link schemes, and spam — tactics that sometimes work briefly and reliably end in penalties.
Measurement Terms
SEO without measurement is guesswork. These are the metrics and tools you'll use to judge whether your work is paying off.
Impressions
An impression is counted every time your page appears in search results for someone, whether or not they click. Rising impressions mean growing visibility — often the first sign an SEO campaign is working, before clicks catch up.
CTR (Click-Through Rate)
CTR is the percentage of people who click your result after seeing it: clicks divided by impressions. If you rank well but your CTR is low, your title and meta description probably need work.
Position
Position is where your page ranks in the results — position 1 is the top organic listing. Average position (reported in Search Console) blends your rank across many queries, so treat it as a trend line rather than a precise number.
Organic Traffic
Organic traffic is the visitors who arrive at your site from unpaid search results. It's the headline metric of SEO — but always pair it with conversions, because traffic that never becomes customers is just a vanity number.
Bounce Rate
Bounce rate is the share of visitors who leave after viewing a single page without interacting. A high bounce rate isn't automatically bad — someone can get their answer and leave satisfied — but paired with short visits, it can signal content that isn't meeting expectations.
Dwell Time
Dwell time is how long a searcher stays on your page before returning to the results. Long dwell time suggests your content satisfied the query; a quick bounce back to Google (called "pogo-sticking") suggests it didn't.
Conversion
A conversion is any valuable action a visitor completes — a purchase, a form submission, a phone call, a booked consultation. Conversions connect SEO effort to revenue, which is why they matter more than any ranking or traffic figure.
Google Search Console
Google Search Console is Google's free tool showing exactly how your site performs in search: which queries you rank for, your impressions, clicks, indexing status, and technical errors. If you install only one SEO tool, make it this one.
Google Analytics
Google Analytics tracks what visitors do after they land on your site — which pages they view, how long they stay, and whether they convert. Combined with Search Console, it gives you the full picture from first impression to final sale.
KPI (Key Performance Indicator)
A KPI is the specific metric you've chosen to judge success — organic traffic, leads, revenue from search. Good SEO reporting picks a small set of KPIs tied to business goals instead of drowning in every available number.
Put the Vocabulary to Work
Fluency in SEO terminology isn't the goal — it's the doorway. Now that you can tell a canonical URL from a 301 redirect and know why E-E-A-T keeps coming up in every algorithm-update recap, the concepts behind everything you read about SEO will click into place faster. The definitions in this glossary cover everything you need to know to follow any SEO conversation, audit report, or how-to guide with confidence.
The best next step is to apply one section at a time: start with keyword research to find your opportunities, use the on-page SEO guide to optimize your pages, and run through the technical SEO audit checklist to catch hidden issues. And if you'd rather skip the learning curve entirely, the Jupiter Digital Marketing team speaks fluent SEO every day — book a free consultation and we'll translate strategy into results for you.