The service is similar to "Likes" in Facebook, where users can "like" pages or comments, showing their appreciation and making them more popular.
Google will have +1 buttons next to all search results and ads and whenever you +1 a link, it is shared via your Google profile.
+1 is intended to personalize search results and ads, due to friends recommending sites.
+1 is the digital shorthand for 'this is pretty cool.' To recommend something, all you have to do is click +1 on a webpage or ad you find useful. These +1's will then start appearing in Google's search results.
Understand better here:
Written by: Andre Yoskowitz @ 30 Mar 2011 21:01