AI search + SEO glossary

AI Overview (AIO) is Google's generative-AI answer panel that appears above blue-link results on Search, composed by Gemini 3 using retrieval-augmented generation over the same Google Search index.

Generative Engine Optimization (GEO) is the practice of optimizing brand visibility within AI search engines like ChatGPT, Google AI Overview, Gemini, Claude, and Perplexity, alongside (not instead of) traditional SEO.

The four-index reality is the structural fact that AI search isn't a single discipline because five major AI search engines source from four distinct underlying indexes — Google (for AIO + Gemini), Bing (for ChatGPT), Brave (for Claude), and Perplexity's own crawler.

Citation rate is the percentage of AI search responses (across queries, platforms, or personas) in which a brand is mentioned, recommended, or linked — the foundational visibility metric for Generative Engine Optimization.

Share of voice in AI search is the percentage of total brand mentions within an AI engine's response set that belong to one specific brand — a competitive measurement complementing the absolute citation rate.

Structured data is machine-readable markup (typically schema.org vocabulary in JSON-LD format) that describes the content and meaning of a webpage to search engines and AI systems — required for rich SERP features, helpful but not required for AI Overview citation per Google's 2026-05-15 guide.

JSON-LD (JSON for Linked Data) is the W3C-standard serialization format for embedding structured data in HTML pages — a JSON object wrapped in a script tag that declares schema.org vocabulary describing the page's content and entities.

GPTBot is OpenAI's web crawler for training data collection, identifiable by the User-Agent string 'GPTBot/1.x' and the published IP range at openai.com/gptbot — distinct from OAI-SearchBot which fetches pages for real-time ChatGPT search citations.

PerplexityBot is Perplexity AI's web crawler that uniquely feeds both training data and Perplexity's live retrieval index in the same crawl event — a dual-horizon bot whose single visit produces both immediate citation visibility and long-term ranking compound.

llms.txt is a proposed AI search standard — a markdown file at the root of a domain that provides curated metadata about the site to AI systems — respected by Anthropic, Perplexity, and OpenAI's GPTBot but explicitly declined by Google as of 2026-05-15.