By using structured data markup you can make your page easily indexable and allow SE bots to better understand your content. In turn, Google can take this data and provide the search engine user with additional small pieces of information right in the SERPs by displaying rich snippets.
Compared to traditional search engine results, a rich snippet can, among else, contain a thumbnail image, review ratings, publication date, additional links or location info. They do not affect your ranking but do increase your CTR.
