Napster was co-founded in 1999 by Shawn Fanning, John Fanning, and Sean Parker and from June 1999 to July 2001 was the easiest way for over 80 million registered users to share their MP3 files with each other. The interface allowed for the saving and sharing of individual songs and accelerated the demise of the complete album as a part of music.
Although the courts shut it down, the Napster brand survived by being bought and sold repeatedly. Napster doesn’t exist anymore, but file sharing lives on. For more information, check out Wikipedia.