It's called +1the 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.
Say, for example, you're planning a winter trip to Tahoe, Calif. When you do a search, you may now see a +1 from your slalom-skiing aunt next to the result for a lodge in the area. Or if you're looking for a new pasta recipe, we'll show you +1's from your culinary genius college roommate. And even if none of your friends are baristas or caffeine addicts, we may still show you how many people across the web have +1'd your local coffee shop.
The beauty of +1's is their relevanceyou get the right recommendations (because they come from people who matter to you), at the right time (when you are actually looking for information about that topic) and in the right format (your search results).
The new button is being rolled out gradually but you can opt in at www.google.com/experimental.
Interestingly, the +1 button will also work on ads. You can learn more about that here.
Take a look at the video below for a demonstration...