Second Life is an online virtual world developed by Linden Lab. It was launched in June of 2003. A number of free client programs, or Viewers, enable Second Life users, called Residents, to interact with each other through avatars. Residents can explore the world (known as the grid), meet other residents, socialize, participate in individual and group activities, and create and trade virtual property and services with one another. As of 2011 Second Life has about one million active users.