Glossary /Structured data
Schema.org
The shared vocabulary, maintained by the major search engines, that defines the types and properties structured data uses.
Schema.org is the agreed dictionary. It defines the types — Article, Product, Organization, FAQPage, DefinedTerm and several hundred more — and the properties each one accepts, so that markup written for one engine is understood by the others. It was founded jointly by Google, Microsoft, Yahoo and Yandex, which is why it functions as a standard rather than a vendor format.
Only a subset of the vocabulary produces visible search features. The rest is still worth using where it is accurate, because it feeds entity understanding and is read by systems beyond the search engines, including the retrieval layers behind assistants.
Choosing the right type matters more than the volume of markup. A page marked up as the type it actually is, with the properties that are genuinely present, does more than a page decorated with every field the validator will accept.