Machine-readable annotation (schema.org, usually in JSON-LD) that states what a page's content is, so engines read defined entities and facts instead of inferring them from prose.
Structured Data, also called schema markup, is machine-readable annotation added to a page that states what its content is: the type of thing described, its properties, and how it relates to other things. It uses the shared schema.org vocabulary, usually written in JSON-LD, so an engine reads a defined entity with explicit fields instead of inferring meaning from prose alone.
In classic search, structured data earns rich results (review stars, FAQs, product prices, event dates) and feeds the knowledge graph with facts a search engine treats as canonical. It is a primary way a brand resolves to a single, correct entity rather than an ambiguous name.
For AI, structured data removes guesswork. A machine reading a page to ground an answer can lift precise, labelled facts rather than parse them out of layout and wording, which lowers the chance of a mistaken or hallucinated attribution. Clear, accurate markup is part of making content easy to retrieve and safe to cite, and so part of AI visibility.
