The area in the video represents the electronic music club scene... a small portion of Second Life. Many of these virtual clubs are filled with live DJs spinning their music or mixing existing music.
The club, textures, and particle effects in the video was created by the residents. 99% of stuff in Second Life is created and owned by the residents.
Second Life is free. You can download the software at no charge, and unless you wish to own land there are no monthly subscriptions fees.
