SEOmoz has created an another excellent infographic on the topic of rich snippets. If you are not familiar with Rich Snippets, take a look at this great documentation by Google.
Snippets—the few lines of text that appear under every search result—are designed to give users a sense for what’s on the page and why it’s relevant to their query.
If Google understands the content on your pages, we can create rich snippets—detailed information intended to help users with specific queries. For example, the snippet for a restaurant might show the average review and price range; the snippet for a recipe page might show the total preparation time, a photo, and the recipe’s review rating; and the snippet for a music album could list songs along with a link to play each song. These rich snippets help users recognize when your site is relevant to their search, and may result in more clicks to your pages.
Google also created this video to explain Rich Snippets in more detail
Below is the SEOmoz infographic that outlines the history and benefits of rich snippets: