If you click on the Search Appearance tab on the side bar of GWT, you’ll see links for Structured Data and Data Highlighter.

Structured data markup lets you add extra data on your pages as it is shown in the Google search results. For instance, IMDB.com attaches movie ratings and # of votes as such:

By going to Structured Data in GWT, you can see the different data types you’ve marked, the # of pages that have marked up data and the items with errors.

By using the Data Highlighter tool, you can mark data on your pages that will teach Google about the pattern of structured data on your website. The supported data types are:
• Articles
• Events
• Local businesses
• Restaurants
• Products
• Software applications
• Movies
• TV Episodes
• Books