From Wikipedia+ (retrieved 2013/07/05):
Google+ (pronounced and sometimes written as Google Plus) is a multilingual social networking and identity serviceowned and operated by Google Inc. It is the second largest social networking site in the world, having surpassed Twitter in January 2013. It has approximately 359 million active users. As of May 2013, it had a total of 500 million registered users, of whom 235 million are active in a given month. Google has described Google+ as a “social layer” that enhances many of its online properties, unlike conventional social networks generally accessed through a single website.