SEO terms, explained simply
The complete, plain-English glossary of 55+ SEO terms - from on-page basics to technical SEO, link building, and the new world of AI search. Search it, skim it, bookmark it.
iWhat is an SEO glossary?
An SEO glossary is a reference that defines the key terms and acronyms used in search engine optimization, so you can understand and apply them. Below you will find 55+ definitions across six categories - each one a short, jargon-free explanation with examples and links to go deeper.
Search the glossary
SEO TitleOn-Page SEOAn SEO title - also called a title tag - is the HTML element that defines the clickable headline a page shows in search engine results.Meta DescriptionOn-Page SEOA meta description is an HTML meta tag that summarises a page in around 120-158 characters.Metadata (in SEO)On-Page SEOMetadata in SEO is the set of HTML tags in a page's <head> that describe the page to search engines and browsers - most importantly the title tag, meta description, robots tag, and viewport.Title TagOn-Page SEOA title tag is the HTML element (<title>) that specifies the title of a web page.Header Tags (H1-H6)On-Page SEOHeader tags (H1 through H6) are HTML elements that define headings and subheadings, creating a hierarchy that organises your content for both readers and search engines.Alt TextOn-Page SEOAlt text (alternative text) is a written description added to an image's HTML that describes what the image shows.Anchor TextOn-Page SEOAnchor text is the visible, clickable words of a hyperlink.URL SlugOn-Page SEOA URL slug is the human-readable part of a URL that identifies a specific page, after the domain and folders.Internal LinkingOn-Page SEOInternal linking is the practice of linking from one page on your website to another page on the same site.Keyword DensityOn-Page SEOKeyword density is the percentage of times a target keyword appears relative to the total word count of a page.Crawling (in SEO)Technical SEOCrawling is the process by which search engines use automated bots (crawlers or spiders) to discover and read pages on the web by following links.Indexing (in SEO)Technical SEOIndexing is the process where a search engine analyses a crawled page and stores it in its index - the massive database it draws on to answer searches.Canonical URLTechnical SEOA canonical URL is the version of a page that you designate as the preferred, master copy when the same or similar content is reachable at multiple URLs.Robots.txtTechnical SEORobots.txt is a plain-text file at the root of a website that tells search engine crawlers which URLs they may or may not request.XML SitemapTechnical SEOAn XML sitemap is a structured file that lists the important URLs on your website, helping search engines discover and crawl them efficiently.Schema MarkupTechnical SEOSchema markup (structured data) is code, usually in JSON-LD format, that labels the content on a page so search engines understand its meaning - for example marking up a recipe, product, FAQ, or breadcrumb.HreflangTechnical SEOHreflang is an HTML attribute that tells search engines which language and regional version of a page to serve to which users.Core Web VitalsTechnical SEOCore Web Vitals are a set of Google metrics that measure real-world user experience for loading performance, interactivity, and visual stability.Page SpeedTechnical SEOPage speed is how quickly a web page loads and becomes usable for a visitor.Mobile-First IndexingTechnical SEOMobile-first indexing means Google predominantly uses the mobile version of a website's content for crawling, indexing, and ranking.Structured DataTechnical SEOStructured data is a standardised format for labelling and organising the information on a page so search engines can understand its meaning.301 RedirectTechnical SEOA 301 redirect is a permanent redirect that sends users and search engines from one URL to another and passes most of the original page's ranking signals to the new URL.CloakingTechnical SEOCloaking is the deceptive practice of showing different content or URLs to search engine crawlers than to human visitors.Broken LinkTechnical SEOA broken link is a hyperlink that points to a page that no longer exists or cannot be reached, usually returning a 404 error.Keyword ResearchContent & KeywordsKeyword research is the process of discovering and analysing the search terms people enter into search engines, so you can create content that targets real demand.Keyword DifficultyContent & KeywordsKeyword difficulty (KD) is a score, usually 0-100, that estimates how hard it would be to rank in the top organic results for a given keyword.Long-Tail KeywordsContent & KeywordsLong-tail keywords are longer, more specific search phrases - usually three or more words - that have lower search volume but clearer intent and less competition.Search IntentContent & KeywordsSearch intent (or user intent) is the underlying goal behind a search query - what the person actually wants.SEO WritingContent & KeywordsSEO writing is the practice of creating content that is optimised to rank in search engines while remaining genuinely useful and readable for people.Topic ClusterContent & KeywordsA topic cluster is a group of interlinked pages covering one subject in depth: a central pillar page covers the broad topic, and cluster pages target specific subtopics, all linking back to the pillar.Pillar PageContent & KeywordsA pillar page is a comprehensive, authoritative page that covers a broad topic in full and links out to more detailed cluster pages on its subtopics.E-E-A-TContent & KeywordsE-E-A-T stands for Experience, Expertise, Authoritativeness, and Trustworthiness - a framework from Google's Search Quality Rater Guidelines used to assess content quality.BacklinkOff-Page SEOA backlink is a hyperlink from another website that points to a page on your site.Link BuildingOff-Page SEOLink building is the process of acquiring backlinks from other websites to your own.White Hat SEOOff-Page SEOWhite hat SEO refers to optimisation tactics that follow search engine guidelines and focus on providing value to users.Black Hat SEOOff-Page SEOBlack hat SEO refers to aggressive tactics that violate search engine guidelines to manipulate rankings.White Label SEOOff-Page SEOWhite label SEO is when one company performs SEO services that another company resells under its own brand.Domain AuthorityOff-Page SEODomain authority is a third-party metric (Moz's DA, and Ahrefs' equivalent Domain Rating or DR) that predicts how well a website can rank, on a 0-100 logarithmic scale based largely on its backlink profile.Reciprocal LinkOff-Page SEOA reciprocal link is a mutual link exchange where two websites link to each other.Digital PROff-Page SEODigital PR is the practice of earning high-authority backlinks, brand mentions, and coverage by promoting newsworthy content - such as original data, studies, and expert commentary - to journalists and publications.Brand MentionOff-Page SEOA brand mention is any reference to your brand on another website or platform, whether or not it includes a link.SERPAnalytics & StrategyA SERP (Search Engine Results Page) is the page a search engine displays in response to a query.Click-Through Rate (CTR)Analytics & StrategyClick-through rate (CTR) is the percentage of people who click your result out of everyone who saw it.Impressions (in SEO)Analytics & StrategyIn SEO, an impression is counted each time one of your pages appears in the search results for a query, whether or not it is clicked.SEO AuditAnalytics & StrategyAn SEO audit is a comprehensive analysis of how well a website is optimised for search engines.SEO VisibilityAnalytics & StrategySEO visibility (or search visibility) is a metric that estimates how prominently a website appears in organic search results across all the keywords it ranks for, weighted by ranking position and search volume.SEO KPIsAnalytics & StrategySEO KPIs (key performance indicators) are the measurable metrics used to track the success of an SEO strategy.PPC (in SEO context)Analytics & StrategyPPC (pay-per-click) is a paid advertising model where advertisers pay a fee each time their ad is clicked - most commonly the ads at the top of search results.SEM (Search Engine Marketing)Analytics & StrategySEM (Search Engine Marketing) is the broad practice of gaining visibility in search engines.Local SEOAnalytics & StrategyLocal SEO is the practice of optimising a business to appear in location-based search results, such as the Google map pack and "near me" searches.Enterprise SEOAnalytics & StrategyEnterprise SEO is the practice of optimising very large websites - often thousands or millions of pages - typically for large organisations.Generative Engine Optimization (GEO)AI SearchGenerative Engine Optimization (GEO) is the practice of optimising your content to be referenced and cited within answers generated by AI search engines and assistants - such as ChatGPT, Perplexity, and Google's AI Overviews.Answer Engine Optimization (AEO)AI SearchAnswer Engine Optimization (AEO) is the practice of optimising content to be served as the direct answer to a question - in featured snippets, voice assistants, and AI answer engines.AI OverviewsAI SearchAI Overviews are AI-generated summaries that appear at the top of Google search results for many queries, synthesising information from multiple sources and linking to them.LLM Optimization (LLMO)AI SearchLLM Optimization (LLMO) is the practice of optimising your content and brand presence so large language models - the AI behind tools like ChatGPT and Gemini - surface and recommend you in their responses.
Showing 55 of 55 terms
How it is organised
The six areas of SEO
Every term in this glossary belongs to one of six areas. Together they cover the whole discipline.
On-Page SEO
Everything on the page itself - titles, metadata, headings, content, and internal links.
Technical SEO
How search engines crawl, render, and index your site - speed, sitemaps, schema, and more.
Content & Keywords
Finding demand and creating content that matches intent and ranks.
Off-Page SEO
Signals from outside your site - backlinks, authority, and brand mentions.
Analytics & Strategy
Measuring what matters - rankings, CTR, visibility, and SEO ROI.
AI Search
The new frontier - GEO, AEO, AI Overviews, and getting cited by AI.
New to SEO?
Start with these six terms
If you are just getting started, learn these fundamentals first - the rest of the glossary will click into place once they do.
SEO Title
An SEO title - also called a title tag - is the HTML element that defines the clickable headline a page shows in search engine results.
Meta Description
A meta description is an HTML meta tag that summarises a page in around 120-158 characters.
Keyword Research
Keyword research is the process of discovering and analysing the search terms people enter into search engines, so you can create content that targets real demand.
Search Intent
Search intent (or user intent) is the underlying goal behind a search query - what the person actually wants.
Backlink
A backlink is a hyperlink from another website that points to a page on your site.
SERP
A SERP (Search Engine Results Page) is the page a search engine displays in response to a query.
Frequently asked questions
What is an SEO glossary?
An SEO glossary is a reference list that defines the key terms, acronyms, and concepts used in search engine optimization - from on-page basics like title tags to technical and AI-search terms - so you can understand and apply them.
How many SEO terms are there?
There is no fixed number, but the essentials that cover most day-to-day SEO fit into a few dozen terms. This glossary defines 55+ of the most important ones across six categories.
What SEO terms should a beginner learn first?
Start with the fundamentals: SEO title, meta description, keyword research, search intent, backlink, internal linking, indexing, and SERP. Once those click, the rest of the glossary makes far more sense.
Is this SEO glossary free?
Yes. Every definition is free to read, with no sign-up. It is maintained by the team behind Soro, the AI that puts your SEO on autopilot.