What structured data actually does

Structured data is a block of machine-readable JSON in the page head describing what the page is: an article with this headline and author, a recipe taking this long, a product at this price.

Search engines use it to show richer results — star ratings, prices, cook times, job listings. It does not change how your page looks to visitors, and it does not directly improve rankings; it makes a page eligible for result formats it otherwise could not appear in.

Each type in the picker says what it gets you, so you can choose by outcome rather than by vocabulary. Google has retired some rich results over the years — FAQ and How-to results, vehicle listings, single course details, the sitelinks search box — and the picker says so for those types. Their markup is still valid and still describes the page; it just no longer earns a different-looking result. Courses now appear only as a carousel of three or more from one site, with a page listing them, which the Course and Item List types say.