Schema.org

It defines types such as Product, Recipe, Event, Person and FAQPage with associated properties. Mark a page up with them and the search engine can tell that "4.7" is a rating rather than a price.

These days it is almost always expressed as JSON-LD in a script tag; microdata and RDFa are the older options. The reward is rich results in search, and more recently that language models can extract facts from the page more reliably.