NBOUND REFERENCE

SEO & GEO Glossary: 30 Terms Defined

Clear definitions for the search and AI visibility terms that matter most in 2026. Covers core SEO concepts alongside the newer GEO, AEO, and AI search vocabulary that is reshaping how brands get found. Updated June 2026.

Jump to: Core SEO Terms · GEO & AEO Terms · AI Search Terms · FAQs

Why SEO and GEO in one glossary? Search and AI answer engines have diverged. A term like “authority” means something slightly different to Google’s ranking algorithm and to ChatGPT’s citation algorithm. Where the meaning differs between SEO and GEO contexts, we say so explicitly. Terms marked [GEO] are specific to AI visibility and generative engine optimisation.

Core SEO Terms

Algorithm

A set of rules and calculations a search engine uses to rank pages in response to a query. Google’s algorithm weighs hundreds of signals including page relevance, authority, speed, and user engagement. Algorithm updates (Core Updates, Helpful Content Updates) can shift rankings significantly. In GEO context, AI engines have their own citation algorithms that weight freshness, structured content, and third-party trust differently from Google.

Authority (Domain Authority / Page Authority)

A measure of how trustworthy and credible a website is perceived to be, primarily based on the number and quality of external links pointing to it. High-authority sites rank more easily for competitive terms. In GEO, authority also influences how often AI engines cite you — brands with strong editorial coverage in trusted third-party sources earn more AI citations. Authority building matters for both SEO and GEO.

Backlink

A link from one website to another. Backlinks are one of the strongest ranking signals in Google’s algorithm because they function as editorial votes of confidence. For GEO purposes, backlinks from high-authority editorial sources also correlate with higher AI citation rates, because AI engines pull from those same sources when forming answers.

Canonicalisation

The process of indicating to search engines which version of a URL is the “master” copy when duplicate or near-duplicate content exists across multiple URLs. Set via a canonical tag (rel="canonical") in the page head. Prevents dilution of ranking signals across duplicate pages.

Click-Through Rate (CTR)

The percentage of people who see a search result and click on it. Calculated as clicks divided by impressions. Average organic CTR has fallen significantly since 2023 as AI Overviews answer queries without requiring a click. 68% of US Google searches ended without a click in the first four months of 2026, according to SparkToro.

Core Web Vitals

Three user experience metrics Google uses as ranking signals: Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and Interaction to Next Paint (INP). Pages that pass Core Web Vitals thresholds receive a ranking benefit. AI crawlers also favour fast, well-structured pages when deciding what to extract and cite.

Crawlability

Whether search engine bots (and increasingly AI crawlers) can access and read a page. Pages blocked by robots.txt, password protection, or JavaScript rendering issues may not be indexed or cited. In 2026, reviewing robots.txt for AI bot access (GPTBot, ClaudeBot, PerplexityBot) is a distinct technical SEO task from standard Google crawlability.

E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness)

Google’s quality framework for evaluating whether content is reliable and useful. E-E-A-T is not a direct ranking signal but influences how Google’s quality raters assess pages. AI engines apply similar criteria when deciding which sources to cite.

Impression

Each time a search result appears on screen, regardless of whether the user clicks. Tracked in Google Search Console. High impressions with low clicks often indicate an AI Overview is answering the query directly — the “AI Overview interception signal.” These keywords are prime GEO targets because being cited inside the AI Overview can recover the engagement lost from zero-click behaviour.

Indexing

The process by which a search engine crawls a page, processes its content, and adds it to the searchable database. A page must be indexed to appear in search results. For GEO, pages that are indexed but not cited by AI engines need a different kind of diagnosis — typically content structure or authority, not crawlability.

Keyword

A word or phrase that searchers type into a search engine. In GEO, the equivalent concept is a “prompt” — the question a user asks an AI engine. The two sets overlap substantially but are not identical; GEO requires optimising for natural-language questions, not just keyword fragments.

Meta Description

A short HTML tag (up to ~160 characters) that describes a page’s content. Not a direct ranking signal, but influences CTR by appearing as the snippet text under a search result title. Google often rewrites meta descriptions if the supplied text doesn’t match the query well.

On-Page SEO

Optimisation work done directly on a page’s content and HTML. Includes title tags, heading structure (H1–H6), keyword placement, image alt text, internal linking, page speed, and structured data markup. On-page SEO is also foundational to GEO: clear heading structure, direct definitions, and FAQ blocks help AI engines extract and cite content correctly.

Organic Search

Search results that appear because of relevance and authority, not paid advertising. The proportion of organic searches that result in clicks to websites has fallen as AI Overviews capture more answers directly in the search results page.

Robots.txt

A text file in a website’s root directory that instructs crawlers which pages or sections they may or may not access. In 2025–26, robots.txt has become an AI visibility concern: blocking GPTBot, ClaudeBot, or PerplexityBot prevents AI engines from reading and citing your content.

Schema Markup

Structured data added to a page’s HTML that tells search engines and AI engines what the content means, not just what it says. Uses the Schema.org vocabulary. FAQPage and DefinedTerm schema directly support AI citation accuracy.

SERP (Search Engine Results Page)

The page displayed by a search engine in response to a query. Modern SERPs include organic results, paid ads, featured snippets, People Also Ask boxes, Knowledge Panels, and AI Overviews. Appearing in SERP features and in AI-generated answers now requires a separate optimisation strategy.

Technical SEO

The work of optimising a website’s infrastructure so that search engines (and AI crawlers) can efficiently crawl, index, and render its content. Covers site speed, mobile-friendliness, structured data, crawl budget, canonicalisation, HTTPS, and URL structure.

GEO & AEO Terms New in AI search

AEO — Answer Engine Optimisation [GEO]

AEO (Answer Engine Optimisation) is the practice of optimising content to appear as direct answers inside AI-powered answer engines — including Google AI Overviews, ChatGPT, Perplexity, and Gemini. AEO focuses on content that AI engines can extract, summarise, and present as a confident response to a user query, with or without a click to the source website.

AI Citation [GEO]

An AI citation is a reference to a specific source (URL or domain) that an AI engine includes when generating a response. Being cited by an AI engine is distinct from ranking in organic search. A brand can rank number one in Google and receive zero AI citations, and vice versa.

AI Overview [GEO]

An AI Overview is a generated summary that appears at the top of some Google search results pages, synthesising information from multiple sources into a direct answer. AI Overviews are triggered on an estimated 20%+ of Google searches as of 2026. Pages that appear as sources inside an AI Overview gain visibility without necessarily receiving clicks.

AI Overview Interception [GEO]

The phenomenon where a Google AI Overview answers a query directly, preventing searchers from clicking through to any website. Identifiable in Google Search Console as a pattern of high impressions with near-zero CTR on informational queries.

Brand Mention (AI) [GEO]

Any appearance of a brand name in an AI-generated response, whether or not the AI includes a source link. Brand mention rate and share of voice are the primary GEO visibility metrics.

Citation Source [GEO]

The specific URL or domain an AI engine cites when including a brand in a response. Citation sources for most B2B brands skew heavily toward third-party sites — review platforms (G2, Capterra), editorial publications, and industry roundups — rather than the brand’s own website.

GEO — Generative Engine Optimisation [GEO]

GEO (Generative Engine Optimisation) is the practice of optimising a brand’s presence to be cited, recommended, and accurately described in AI-generated answers from platforms including ChatGPT, Perplexity, Gemini, Google AI Overviews, and Claude. GEO is an emerging discipline that emerged as a distinct field in 2024.

GEO Score [GEO]

A composite metric used to benchmark a brand’s AI visibility across multiple dimensions. NBound’s GEO Score assesses five factors: AI citation rate, content structure quality, technical AI foundation, off-site citation authority, and brand consistency across platforms. See Managed GEO Services.

Prompt (AI search) [GEO]

In the GEO context, a prompt is a natural-language question or instruction that a user submits to an AI engine. Prompts are the GEO equivalent of keywords in SEO: the unit of query around which visibility is measured and optimised.

Sentiment (AI) [GEO]

In GEO monitoring, sentiment refers to whether an AI engine describes a brand positively, neutrally, or negatively when it appears in a response. Brand misrepresentation in AI engines is an emerging reputation risk that GEO programmes actively monitor and correct.

The proportion of AI responses to a set of tracked prompts in which a brand appears, relative to competitor brands. GEO monitoring platforms including Peec AI, Profound, and Scrunch AI all track share of voice as a core metric. See our GEO software comparison.

Zero-Click Search [GEO]

A search that is resolved without the user clicking through to any website. 68% of US Google searches ended without a click in early 2026, according to SparkToro research. Zero-click growth is the primary commercial driver for GEO investment.

AI Search Terms

AI Search

AI search refers to search interfaces that generate natural-language answers to queries rather than returning a ranked list of links. Perplexity, ChatGPT Search, Google AI Overviews, and Gemini all represent forms of AI search. The key distinction from traditional search: AI search synthesises an answer; traditional search ranks sources for the user to evaluate.

Large Language Model (LLM)

A large language model is a type of AI trained on vast quantities of text data to predict and generate language. LLMs power AI search engines including ChatGPT (GPT-4o), Gemini, Claude, and the models underlying Perplexity. When an LLM generates an answer that includes a brand citation, it is drawing on patterns in its training data and, where retrieval-augmented generation (RAG) is used, on live web content fetched at query time.

LLM Crawler / AI Bot

A web crawler operated by an AI company to retrieve and index web content for use in LLM training or retrieval-augmented generation. Major AI crawlers include GPTBot (OpenAI), ClaudeBot (Anthropic), PerplexityBot, and GoogleBot-Extended (Google AI). Sites can allow or block these crawlers via robots.txt.

RAG — Retrieval-Augmented Generation

Retrieval-Augmented Generation (RAG) is a technique where an AI model retrieves relevant documents from the web (or a database) at query time before generating its response. RAG enables AI engines to give answers based on current web content rather than relying entirely on training data. Perplexity uses RAG by default. ChatGPT uses it when web browsing is enabled.

UI Scraping (GEO monitoring)

A methodology used by some GEO monitoring platforms to track AI visibility. Instead of querying an AI engine’s API, UI scraping simulates a real user session and captures what the AI actually displays. Peec AI and Scrunch AI use UI scraping; Ahrefs Brand Radar uses a keyword-database approach. See our GEO software feature comparison.

QUICK REFERENCE

SEO vs GEO: the key differences at a glance

Goal: SEO — rank in Google’s blue links. GEO — get cited in AI-generated answers.

Measurement: SEO — keyword rankings, organic traffic, CTR. GEO — brand mention rate, share of voice, citation source coverage.

Key signals: SEO — authority (backlinks), relevance (keywords), technical quality. GEO — freshness, structured formatting, third-party editorial citations, brand consistency.

Where they overlap: Both reward content that is authoritative, accurate, and well-structured. Technical issues (blocking crawlers, poor structure) hurt both.

The gap: A brand can rank page one in Google and have zero AI citations. Closing that gap requires GEO work. See Managed GEO Services →

FAQ

Common questions.

What is the difference between SEO and GEO?

SEO (Search Engine Optimisation) is the practice of optimising content to rank in traditional search engine results pages. GEO (Generative Engine Optimisation) is the practice of optimising content to be cited in AI-generated answers from platforms like ChatGPT, Perplexity, Gemini, and Google AI Overviews. The goal of SEO is a ranking; the goal of GEO is a citation. The signals that drive each outcome differ: SEO rewards authoritative backlinks and keyword relevance; GEO rewards freshness, structured content, and third-party editorial mentions.

What is AEO and how is it different from GEO?

AEO (Answer Engine Optimisation) focuses specifically on appearing as direct answers inside AI-powered answer tools. GEO is the broader practice that includes AEO alongside citation tracking, competitive analysis, off-site authority building, and technical optimisation for AI crawlers. In practice, most GEO programmes include AEO tactics as part of their content strategy.

What is a zero-click search?

A zero-click search is a search query that is resolved without the user clicking through to any website. SparkToro research found that 68% of US Google searches in early 2026 ended without a click. Zero-click growth is the primary driver for GEO investment: when buyers research your category by asking an AI engine, your visibility must exist in AI-generated answers, not just organic rankings.

What is schema markup and why does it matter for GEO?

Schema markup is structured data added to a page’s HTML using the Schema.org vocabulary. It tells search engines and AI engines what the content means, not just what it says. For GEO, the most important schema types are FAQPage (which helps AI engines extract question-and-answer pairs), DefinedTerm (which identifies glossary definitions for extraction), and Article (which signals that content is editorial and dated).

What is E-E-A-T and does it affect AI citations?

E-E-A-T stands for Experience, Expertise, Authoritativeness, and Trustworthiness. While it is not a direct algorithmic ranking signal, it influences how Google evaluates content quality. AI engines apply similar (though not identical) criteria when selecting sources to cite: they favour content from sources with demonstrated expertise, third-party validation, and accurate factual claims.

How do AI crawlers work and can I block them?

AI crawlers are web bots operated by AI companies to retrieve and index web content. Major crawlers include GPTBot (OpenAI), ClaudeBot (Anthropic), PerplexityBot, and Google-Extended. Yes, you can block them in your robots.txt file — but doing so prevents your content from being read and cited by the associated AI engine. Many sites inadvertently block AI crawlers through outdated robots.txt configurations.