While Google has primarily been the innovator, it has now decided to borrow an idea from someone else. The "like" option on Facebook is obviously the inspiration behind the move and the "+1" will function in a similar manner. If you click the "+1" button for a website, the page in question is linked and displayed on your profile. You can also use the option for Google Ads.
Google Blog - The beauty of +1’s is their relevance - you 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).
Currently, the +1 does not work entire as an "up-vote" since it does affect the search order or increase the visibility of any website or ad most likely to deter exploitation by spammers. More information, straight from the horse's mouth can be found here. And for those who want to try out the feature for themselves, they can opt in to the Google Experiment now.