When you use structured data to mark up a website, you help Google understand its context for display in Search, and you achieve better distribution of your content to users from Search. Meaning, you typically will rank higher in the results. You do this by marking up content properties and enabling actions where relevant. This makes that content eligible for inclusion in rich results. For some content types, it allows users to engage directly with your content right from Search which saves the viewers of your content a click, putting you ahead of your competition.
A variety of content types qualify to appear in rich results. CreativeWork is a schema.org type definition that applies to qualifying content produced for reading, viewing, listening or other consumption, such as news articles, recipes, and videos. Other content types, such as products and local business listings, belong to the commerce category, which is a custom category we use to describe schema.org types generally intended for retail purposes.
Some of the content types that Google uses are below:
To learn more about Rich Snippets in search read this article from Google.