What are Rich snippets actually? They are the few lines of text or icons that are displayed under the title of each search result. These are intended to give users an idea of what is on the page and why the page is relevant to their search query. If Google understands the content on your pages, it can create rich snippets. These are snippets with detailed information designed to help users with specific search queries. For example, the snippet for a restaurant may display the average review score and price, the snippet for a recipe page may show the total preparation time, a photo, and the review score of the recipe, and the snippet for a music album could contain a list of tracks, along with a link to play each track. These rich snippets help users determine if your site is relevant to their search and can lead to more clicks to your pages.

Yes, that's great, but how do I get that done? Here are the three steps to adding 'rich snippets' (or standardized HTML tags) to my HTML code.
1. Select a markup format.
Google recommends using microdata, but all three formats listed below are accepted. You do not need to have background knowledge of these formats; you only need a general knowledge of HTML.
Microdata (recommended)
2. Mark up your content.
Google supports rich snippets for these content types:
Google can also recognize labels for video content and we use these to improve our search results.
3. Test your markups.
Use the structured data testing tool to ensure that Google can read and extract your marked-up data.
That's it. Once you have added and tested your rich snippets markups, Google will discover them the next time your site is crawled. A few things to keep in mind:
It may take some time for rich snippets to appear in search results or on Places pages.
If no rich snippets are displayed for your site, you can view possible reasons for this.
Marking up your data for rich snippets does not affect the position of your page in search results. Google also cannot guarantee that your markups will be used.
For more information, also visit the website of http://schema.org