Schema markup
Also known as: Structured data, JSON-LD
Schema markup is code added to a page that describes the meaning of its content using the shared vocabulary published at schema.org.
In full
Schema markup, also called structured data, is machine-readable code added to a web page that labels what its content means rather than leaving it to be inferred. It uses a shared vocabulary published at schema.org and developed jointly by Google, Microsoft, Yahoo, and Yandex. Rather than a search engine guessing that a string of digits is a phone number, schema states it explicitly. The recommended format is JSON-LD, which sits in a script tag separate from the visible markup, so redesigning a page does not silently break the data. Useful types for a business include Organization, LocalBusiness, Article, Product, Service, Person, and BreadcrumbList.
Why it matters
Structured data is how a machine becomes confident about who you are and what you offer. Organization markup with accurate sameAs links is the mechanism by which systems resolve that your website, your profiles, and mentions of you elsewhere are all the same entity.
A common misconception
That schema markup improves rankings or reliably drives AI citations. Google states it is not a ranking factor, and research on AI citation finds the benefit comes from markup carrying concrete values such as real prices and dates, not from the presence of tags.