Schema.org is a shared vocabulary co-built by Google, Microsoft, Yahoo, and Yandex. It defines how a page can declare what kind of thing it is, what it knows, what it links to, and how it relates to other things. The model reads JSON-LD, a small block of structured data in the head of your page, and pulls a complete entity definition from it without having to parse prose.
Without schema, the model guesses. With schema, the model is handed a definition. That single difference triples AI citation rates on the same content.
Seventeen types matter for an expert site: Person, Organization, Article, BlogPosting, FAQPage, HowTo, Review, Course, Event, Service, BreadcrumbList, VideoObject, ImageObject, AboutPage, ContactPage, Offer, and WebSite. You do not need all seventeen on day one. You need Person on the homepage and About page, Article on every blog post, FAQPage on the FAQ block, and BreadcrumbList on every page. Those four cover roughly ninety percent of what a model wants from a knowledge-led site.
The single most important field on Person is sameAs. It accepts an array of URLs that link your domain identity to your LinkedIn profile, your YouTube channel, your Wikidata entry, your podcast feed, and any other verified surface. AI engines treat sameAs as identity proof: one entity confirmed across multiple sources. This is the field where Ring 1 starts pulling Ring 2 into a single coherent picture.