Schema markup is a great tool that Google, Yahoo, and Microsoft introduced to help their search engines better identify what specific site elements are. You often see it cited for sites focused on a certain kind of content. For example, a food blog can use schema markup to flag ingredients, instruction steps, nutritional values, and tags like «vegan» or «keto» on their recipes. Likewise, a review blog can flag the star or numerical reviews they create for individual sections or products as a whole.
The schema data allows Google to use it as part of a rich snippet. For example, when you search for a recipe with a specific identifier, Google will show a few rich snippets with that identifier pulled from the schema data. It’s pretty useful.