"Structured data markup" is a standard way to annotate your content so machines can understand it. When your web pages include structured data markup, Google (and other search engines) can use that data to index your content better, present it more prominently in search results, and surface it in new experiences like voice answers, maps, and Google Now.
Especially this feature:
To make your pages eligible for Rich Snippets in search results, add structured data of the appropriate type to your content. Make sure to comply with any policies that each type has regarding Rich Snippet display. Google supports Rich Snippets for the following data types:
Product -- Information about a product, including price, availability, and review ratings.
Recipe -- Recipes that can be displayed in web searches and Recipe View.
Review -- A review of an item such as a restaurant, movie, or store.
Event -- An organized event, such as musical concerts or art festivals, that people may attend at a particular time and place.
SoftwareApplication -- Information about a software app, including its URL, review ratings, and price.
Video -- An online video, including a description and thumbnail.
News article -- A news article, including headline, images, and publisher info.