Second Life Description from Wikipedia

"Second Life (abbreviated as SL) is an Internet-based virtual world which came to international attention via mainstream news media in late 2006 and early 2007.^[4][5] Developed by Linden Research, Inc (commonly referred to as Linden Lab), a downloadable client program enables its users, called "Residents", to interact with each other through motional avatars, providing an advanced level of a social network service combined with general aspects of a metaverse. Residents can explore, meet other Residents, socialize, participate in individual and group activities, create and trade items (virtual property) and services from one another."

http://en.wikipedia.org/wiki/Second_Life