Web 2.0 is a buzzword that encompasses a lot of concepts and doesn't have a comprehensive definition. Wikipedia says: "Web 2.0, a phrase coined by O'Reilly Media in 2004, refers to a perceived or proposed second generation of Web-based services—such as social networking sites, wikis, communication tools, and folksonomies—that emphasize online collaboration and sharing among users." Here's a visually-brilliant video that tries to define Web 2.0 in less than 5 minutes. Video after the jump.

Web 2.0, Visual Explanation, Online Video