Rich snippets can relate: reviews, people profiles, businesses & organizations or events, making search results look more relevant. The more information a search result snippet can provide, the easier it is for users to decide whether that page is relevant to their search. The improved listing is called a rich snippet, and can appear on google search results pages or on Place Pages in Google Maps.
Image below displays a rating & price range (useful to anyone searching for information about a restaurant)
Google currently supports the following information types: reviews, people profiles, business listings, and events. For rich snippets you can mark up your structured HTML content any of three formats: microdata, RDFa, or microformats.
Rich snippet with microdata:
<div itemscope itemtype="http://data-vocabulary.org/Person"> My name is <span itemprop="name">Emilian Robert Vicol</span> but people call me <span itemprop="nickname">ByREV</span>. Here is my home page: <a href="http://byrev.org" itemprop="url">byrev.org</a> I live in Tg_jiu, GJ and work as an <span itemprop="title">freelancer</span> at <span itemprop="affiliation">Home</span>. </div>
You can find more information about Rich snippets here : http://www.google.com/support/webmasters/…