Google are constantly striving to present searchers with the most informative and useful results and it is with this in mind that they first introduced ‘rich snippets’ for search in May 2009.
Initially rich snippets were introduced for reviews and people profiles. Now rich snippets can be used for the likes of these along with events, products, videos, recipes and business listings.
It is likely that you may have come across rich snippets in search without realising. The rich snippet can show in light grey or as a star rating (if it is a review), between the hyperlink and the short description in search results, such as this:

Rich snippets are allowing users to make a decision from the search results page on whether or not they want to find out more by clicking through to that website.
Who can use rich snippets?
Rich snippets can be used by Webmasters who have websites which offer the following kinds of information:
Rich Snippets make it possible to label these pieces of information within the website source code (using Microdata, Microformat or RDFa formats) to show Google that this information represents a certain type of data (click on one of the above to see what code to insert). To ensure that you have entered the code correctly within your site Google offer the Rich Snippets Testing Tool.
Why use rich snippets?
The answer to why you would want to use these is simple; by telling Google exactly what it is that you have to offer their searchers you are helping them to better recognise and display your information in search results.
Rich Snippets are one of the easiest ways to offer organised and optimised data to the Search Engines and by doing so you enhance the display of your site in organic search results. This in itself could help to improve the organic click through rate for your site.
How do rich snippets affect local search?
We are seeing Google make changes to the way that search results are showing for local searches, with Place Search, where Google Places listings are now showing in the top of the search results and it is because of this that webmasters should take advantage of rich snippets within their websites from now on to ensure that they are providing the most information that they can about their site and what it has to offer the user.
When it comes to local search results, Google source the best information that they can for your search however there are missed opportunities for your website when this information isn’t clearly presented. Google Places pages often show references to particular businesses from other websites, but for Google to be able to find these pages they need to be able to understand your reference to the site – and that is where structured rich snippets markup comes in.
Rather than having strings of unstructured text on your website, which Google does not recognise – help them out by inserting Rich Snippets and give your website structured content.