- Second Life is a 3D virtual world launched in 2003 that has over 15 million users who use customizable avatars to interact and create using an in-world economy. - It is unique from other virtual worlds in that it uses distributed simulation across multiple servers allowing for continuous expansion and advanced compression allowing thousands of objects to stream smoothly. - Within Second Life, various universities, organizations, and individuals use it for networking, collaboration, education, psychotherapy, and more.