Second Life is an online virtual world, developed by Linden Lab, based in San Francisco, and launched on June 23, 2003. By 2013 Second Life had approximately 1 million regular users, according to Linden Lab, which owns Second Life. In many ways, Second Life is similar to MMORPGs (Massively Multiplayer Online Role Playing Games); however, Linden Lab is emphatic that their creation is not a game: "There is no manufactured conflict, no set objective".
The virtual world can be accessed freely via Linden Lab's own client programs, or via alternative Third Party Viewers. Second Life users (also called Residents) create virtual representations of themselves, called avatars and are able to interact with other avatars, places or objects. They can explore the world (known as the grid), meet other residents, socialize, participate in individual and group activities, build, create, shop and trade virtual property and services with one another. It is a platform that principally features 3D-based user-generated content. Second Life also has its own virtual currency, the Linden Dollar, which is exchangeable with real world currency. Second Life is intended for people aged 16 and over, with the exception of 13–15-year-old users restricted to the Second Life region of a sponsoring institution (e.g. school).
Built into the software is a three-dimensional modeling tool based on 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, 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 (DRM) functions. However, Linden Lab changed their terms of service in August 2013, to be able to use user-generated content for any purpose. The new terms of service prevent users from using textures from 3rd-party texture services, as some of them pointed out explicitly. Users can also photograph in Second Life with the camera technology the client programs have.
(Source: Wikipedia https://en.wikipedia.org/wiki/Second_Life)