Definition: User generated Content refers to various kinds of media content, publicly available, that are produced by end-users. The term entered mainstream usage during 2005 after arising in web publishing and new media content production circles.
It reflects the expansion of media production through new technologies that are accessible and affordable to the general public. These include digital video, blogging, podcasting, news, gossip, research, mobile phone photography and wikis. In addition to these technologies, user generated content may also employ a combination of open source, free software, and flexible licensing or related agreements to further diminish the barriers to collaboration, skill-building and discovery.
(Source: Wikipedia)