SEO Terms, Explained Plainly

Plain definitions for the SEO terms that come up most, with links to fuller explanations where there's more to say. No padding, no invented jargon.

Crawling and indexing

• Crawling — a search engine bot requesting your pages and following links to discover more.
• Indexing — the search engine deciding to store a crawled page so it can appear in results. Crawled does not mean indexed.
• Crawl budget — how many pages a search engine will crawl in a given period. Largely irrelevant below roughly 10,000 pages.
• robots.txt — a file at your domain root telling crawlers what not to crawl. It prevents crawling, not indexing.
• noindex — a meta tag telling search engines not to store a page. The page must be crawlable for this to be seen.
• XML sitemap — a machine-readable list of your indexable URLs. Aids discovery; does not force indexing.
• Canonical tag — declares which URL is the authoritative version when the same content is reachable at several addresses.

On-page terms

• Title tag — the page title shown in search results. Roughly 60 characters before truncation.
• Meta description — the summary beneath the title in results. Not a ranking factor; strongly affects click-through rate.
• H1 — the main heading. One per page.
• Alt text — a description of an image for screen readers and search engines. Describe the image; don't stuff keywords.
• Internal link — a link between pages on your own site. One of the most underused SEO levers.
• Anchor text — the visible clickable text of a link. Descriptive beats "click here."

Technical terms

• Core Web Vitals — LCP (loading), INP (responsiveness), CLS (visual stability).
• LCP — Largest Contentful Paint. Time until the main content appears. Target 2.5 seconds or less.
• INP — Interaction to Next Paint. Responsiveness to input. Target 200ms or less. Replaced FID in 2024.
• CLS — Cumulative Layout Shift. How much the layout jumps while loading. Target 0.1 or less.
• Structured data — machine-readable markup (usually JSON-LD) describing what a page is. See schema.org.
• Mobile-first indexing — Google indexes and ranks the mobile version of your page.
• Rendering — how a browser or crawler turns HTML, CSS, and JavaScript into a finished page. Content requiring JavaScript may be missed.
• 301 / 302 — permanent and temporary redirects. Use 301 for permanent moves; it passes ranking signals.

Fuller treatment: the technical SEO map.

Off-page and strategy

• Backlink — a link to your site from another domain.
• White hat / black hat — methods search engines endorse versus methods that exploit gaps. See the comparison.
• Search intent — what the searcher actually wants: information, comparison, or to take action.
• SERP — Search Engine Results Page.
• Featured snippet — an answer box shown above the standard results.
• E-E-A-T — Experience, Expertise, Authoritativeness, Trustworthiness. Concepts from Google's quality rater guidelines, not a direct ranking score.
• AEO / GEO — Answer Engine and Generative Engine Optimization. See SEO vs GEO vs AEO.

Related reading: SEO principles, the metrics worth tracking, and common SEO questions.