Second Life, often referred to by its users simply as SL, is an Internet-based virtual world which entered the mainstream in late 2006. Developed by Linden Lab, a downloadable program enables its users, called "Residents," to interact with each other through on-screen characters known as avatars. The SL world provides an advanced level of a social network service as Residents can explore, meet other Residents, socialize, participate in individual and group activities, create and trade items (virtual property) and services from one another.

Second Life is not a game even though it is sometimes referred to as such. It does not have points, scores, winners or losers, levels, an end-strategy, etc. As of today, more than six million accounts have been registered although many are not active and and some Residents have multiple accounts. Competitors include Active Worlds, There, Entropia Universe, Dotsoul Cyberpark, Red Light Center, and Kaneva