Schema.org

Schema.org is the collaborative vocabulary that defines the types and properties used in structured data. Launched in 2011 by the major search engines, it provides a shared set of terms, Thing, Organization, Person, Product, Article, LocalBusiness, Event, Recipe, and hundreds more, each with defined properties and relationships. When you mark up a page with JSON-LD, you are using Schema.org types.

The vocabulary is a living spec; new types and properties are added, and some are deprecated. This is why validating against the current spec matters: a property that was valid in a 2020 example may have changed, and Google's own rich-result requirements evolve independently of the broader vocabulary. We validate against the live spec rather than a frozen copy.

For most sites, a small set of types carries most of the value: Organization and WebSite on the homepage, Article on editorial content, Product and Offer on commerce pages, LocalBusiness with its subtypes for physical businesses, FAQPage and HowTo where applicable, and BreadcrumbList for navigation. The art is choosing the most specific accurate type, a Personal Injury Attorney is better described by LegalService than by the generic LocalBusiness, because specificity is what helps an engine place your entity correctly.