Tencent QQ, generally referred to as QQ, is the most popular free instant messaging computer program in mainland China. As of July 11, 2011, the active QQ users accounts for QQ IM totaled 812.3 million, possibly making it the world's second largest online community. The number of simultaneous online QQ accounts exceeded 100 million. In February 2011, QQ.com ranked 10th overall in the Alexa Internet rankings just behind Twitter ranked 9th. The program is maintained by Tencent Holdings Limited, owned in part by Naspers. Since its entrance into Chinese households, QQ quickly emerged as a modern cultural phenomenon, now being portrayed in popular culture. Aside from the chat program, QQ has also developed many subfeatures including games, virtual pets, ringtone downloads, blogs, etc.

Source: Wikipedia