Reference

SEO Glossary 2026

Every term you need — from robots.txt fundamentals to GEO and AI Overviews. Terms marked with a chapter link are playable scenarios in the game.

Technical SEO

robots.txt: A plain-text file at your domain root that instructs search engine crawlers which pages to crawl or skip. A single misconfigured `Disallow: /` can make an entire site invisible.
XML Sitemap: A structured list of your site's URLs that helps search engines discover and index pages. Submit via Google Search Console for fastest indexing.
noindex: An HTML meta tag (`<meta name="robots" content="noindex">`) or HTTP header that tells search engines not to include a page in their index.
Canonical Tag: A `<link rel="canonical">` element that tells search engines which URL is the preferred version when duplicate or near-duplicate content exists.
Soft 404: A page that returns an HTTP 200 status code but displays a "not found" or empty message. Google treats these poorly — they waste crawl budget and dilute index quality.
Core Web Vitals: Google's user experience metrics: Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). Part of the Page Experience ranking signal.
Crawl Budget: The number of pages Googlebot will crawl on your site within a given time. Large sites with poor internal linking and lots of duplicate content waste crawl budget.
Rendering: The process by which a browser or crawler executes JavaScript to build the DOM. Client-side rendered (CSR) content can be missed by crawlers if not handled with SSR or pre-rendering.

Backlink: A hyperlink from another website pointing to yours. Backlinks are a core ranking signal — quality and relevance matter far more than quantity.
Referring Domain: A unique website that links to yours at least once. 100 links from 1 domain is worth far less than 10 links from 10 unique high-quality domains.
Domain Authority (DA): A third-party metric (Moz) estimating how likely a domain is to rank in search results, based on its backlink profile. Correlates with but doesn't directly affect rankings.
Disavow File: A text file submitted to Google via the Search Console Disavow Tool, listing domains or URLs whose links you want Google to ignore. Used to address unnatural link penalties.
Manual Action: A penalty applied by a human Google reviewer, not an algorithm. The most common type: 'Unnatural links to your site.' Requires a reconsideration request after cleanup.
Negative SEO: A black-hat attack where a competitor builds toxic backlinks to your site to trigger a manual penalty or algorithmic demotion.
Link Velocity: The rate at which a site acquires new backlinks over time. A sudden spike from low-quality domains is a strong spam signal.
Anchor Text: The clickable text of a hyperlink. Over-optimized exact-match anchors (e.g. 300 links all saying 'buy cheap shoes') is a major unnatural link signal.

Schema Markup: Structured data added to HTML (usually as JSON-LD) using Schema.org vocabulary. Enables rich results like star ratings, FAQs, and product prices in the SERP.
Entity SEO: Optimizing for entities — people, places, organizations, products — rather than keywords. Google's Knowledge Graph is built on entities, not keyword strings.
Topical Authority: Google's assessment of a site's comprehensive coverage of a subject. Sites with deep, inter-linked content clusters on a topic rank better than thin, scattered content.
Knowledge Graph: Google's database of interconnected entities and their relationships. Being an entity in the Knowledge Graph improves brand SERP features like knowledge panels.
E-E-A-T: Experience, Expertise, Authoritativeness, Trustworthiness — Google's framework for evaluating content quality. Strong E-E-A-T signals include named expert authors, citations, and off-site mentions.
Content Cluster: A group of closely related pages covering a topic comprehensively — a pillar page + cluster articles — connected by internal links. The structure signals topical depth to Google.
Keyword Cannibalization: When multiple pages on your site compete for the same search intent, splitting click-through rates and ranking potential. Solved through consolidation or intent differentiation.

AI Overview (AIO): Google's AI-generated summary answer appearing at the top of search results. AIOs can displace #1 organic rankings — the site cited in the AIO captures trust but may lose direct traffic.
GEO (Generative Engine Optimization): The practice of optimizing content to be cited by AI-generated search answers (Google AIOs, Perplexity, ChatGPT Search). Focuses on direct answers, citations, and entity clarity.
Zero-Click Search: A search query that is answered entirely on the SERP — via AI Overviews, featured snippets, or knowledge panels — without the user clicking through to any website.
LLM Citation: When a large language model (ChatGPT, Perplexity, Gemini) references your site as a source in its generated answers. Requires being in LLM training data or live-search index.
Share of Voice (AI): The percentage of AI-generated answers in your niche that mention or cite your brand vs. competitors. A new SEO KPI for the generative search era.
BOFU (Bottom of Funnel): Content targeting users ready to buy or decide (e.g. product comparisons, pricing pages, reviews). Less vulnerable to AI Overview displacement than TOFU how-to content.
Featured Snippet: An organic result highlighted in a box at position zero, showing a direct answer extracted from the page. Winning a featured snippet often requires structured, question-answer formatted content.

The best way to understand these concepts is to live through a disaster.