Back in March of 2011, Google announced their new +1 button which would show up in the search results. This new button would allow you to "like" a web page that shows up in the results and thus give it a vote in favor of the search term you are querying.
More recently however, Google has announced that the +1 button can be used on any website. They have some code that you can add to your page and the button will appear for your visitors to vote in your favor. This can be another signal that Google will use in their coveted and complex ranking algorithm to display search engine results pages (SERPs).
Google states:
Adding +1 buttons to your pages is a great way to help your content stand out in Google search. By giving your visitors more chances to +1 your pages, your search results and search ads could show up with +1 annotations more often, helping users see when your pages are most likely to be useful.