Google +1 is yet another effort to make Google more social. It's Google's description of the Facebook "likes", a simple feature that's very powerful because it's part of a social network.
Google will show +1 buttons next to all look for results and ads, while encouraging other sites to include the buttons. All +1's are public and they're tied to Google Profiles. The goal is to use this data to personalize look for results and ads by recommending sites +1'd by your friends. Google Social Search already does this, but there's no hold up for Facebook likes, so Google had to come up with a substitute.
"+1 is the digital shorthand for 'this is pretty cool.' To advocate 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," explains Google.
This feature is gradually rolled out to Google.com, but you can try it by enabling the +1 search experiment.
One thing is clear: Google won't have to translate "+1" when it will restrict the service, but it will have a hard time translating "+1's", "+1'd" and other cryptic constructs. Google +1's URLs previously look weird (here's the homepage: http://www.google.com/+1).
Your +1's are scheduled in a profile tab, where you can manage them. There's also a page that lets you disable personalizing Google ads using +1's and other in order from your Google profile.
Google now has the most significant pieces of a social network (profiles, activity stream, likes, apps), but there's still no social network, no magic "glue" that connects the existing pieces. As Danny Sullivan explains, the "+1 social network" is made up of your Google Talk friends, the people from Gmail's "My contacts" group and the people you go behind in Google Reader and Google Buzz, but you'll soon be able to attach other services like Twitter and Flickr. It's actually a meta social network, an artificial service that won't have too numerous enthusiastic users, just like Friend Connect.