Second Life is an online virtual world developed by Linden Lab. It was launched on June 23, 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. Second Life is intended for people aged 16 and over,and as of 2011 has about one million active users.
Built into the software is a three-dimensional modeling tool based around simple geometric shapes that allows residents to build virtual objects. There is also a procedural scripting language, Linden Scripting Language, which can be used to add interactivity to objects. Sculpted prims (sculpties), mesh, textures for clothing or other objects, and animations and gestures can be created using external software and imported. The Second Life Terms of Service provide that users retain copyright for any content they create, and the server and client provide simple digital rights management functions

In 1999, Philip Rosedale formed Linden Lab. He made Second Life, developing computer hardware allowing people to immerse in a virtual world. In its earliest form, the company struggled to produce a commercial version of the hardware, known as « The Rig », which was realized in prototype form as a clunky steel contraption with computer monitors worn on shoulders. That vision changed into the software application Linden World, in which people participated in task-based games and socializing in a three-dimensional online environment. That effort would eventually transform into the better known, user-centered Second Life. Although he was familiar with the metaverse of Neal Stephenson’s novel Snow Crash, Rosedale has said that his vision of virtual worlds predates that book, and that he conducted early virtual world experiments during college years at the University of California San Diego, where he studied physics.
On December 11, 2007, Cory Ondrejka, who helped program Second Life, was forced to resign as chief technology officer.
In January 2008, residents spent a total of 28,274,505 hours « inworld », and, on average, 38,000 residents were logged in at any particular moment. The maximum concurrency (number of avatars inworld) recorded is 88,200 in the 1st qtr. 2009
On March 14, 2008, Rosedale announced plans to step down from his position as Linden Lab CEO and to become chairman of Linden Lab’s board of directors.Rosedale announced Mark Kingdon as the new CEO effective May 15, 2008. In 2010, Kingdon was replaced by Rosedale, who took over as Interim CEO. After four months though, Rosedale abruptly stepped down from the Interim CEO position. It was announced in October 2010, that Bob Komin, Linden Lab’s chief financial officer and chief operating officer, will take over the CEO job for the immediate future.
In 2008, Second Life was honored at the 59th Annual Technology & Engineering Emmy Awards for advancing the development of online sites with user-generated content. Rosedale accepted the award.
In May 2009 concurrent users averaged about 62,000. As of May 2010 concurrent users averaged about 54,000. The perceived decline in median concurrent users over this time correlates precisely with new policies implemented by Linden Lab reducing the number of bots and campers.
In June 2010, Linden Labs announced layoffs of 30% of its workforce.
In November 2010, 21.3 million accounts were registered, although there are no reliable figures for actual long-term consistent usage.

Second Life has an internal economy and internal currency, the Linden dollar (L$). L$ can be used to buy, sell, rent or trade land or goods and services with other users. Virtual goods include buildings, vehicles, devices of all kinds, animations, clothing, skin, hair, jewelry, flora and fauna, and works of art. Services include « camping », wage labor, business management, entertainment and custom content creation (which can be broken up into the following 6 categories: building, texturing, scripting, animating, art direction, and the position of producer/project funder). L$ can be purchased using US Dollars and other currencies on the LindeX exchange provided by Linden Lab, independent brokers or other resident users. Money obtained from currency sales is most commonly used to pay Second Life’s own subscription and tier fees; only a relatively small number of users earn large amounts of money from the world. According to figures published by Linden Lab, about 64,000 users made a profit in Second Life in February 2009, of whom 38,524 made less than US$10, while 233 made more than US$5000. Profits are derived from selling virtual goods, renting land, and a broad range of services.