Glossary
Schema.org
Schema.org is a shared vocabulary of types and properties, maintained collaboratively by major search engines, used to describe the meaning of web content in a machine-readable way.
It provides the nouns — Organization, Product, LocalBusiness, FAQPage, Person — and the properties that describe them. Publishers embed these as JSON-LD so machines can parse meaning rather than infer it.
Choosing the most specific applicable type matters. A law firm marked up as Organization is understood generically; the same firm marked up as LegalService carries its category in the data itself.
Why it matters
It is the common language every major engine already understands. Using it correctly is the difference between describing your business and merely mentioning it.