web 2.0 was first mentioned in 1999 by  Darcy DiNucci, then further popularized by Tim O'Reilly. Web 2.0 is a change in the way webpages are made and use, technology beyond the basic pages of earlier web sites. Web 2.0 can be used to describe webpages that allow the users to interact and collaborate with each other in social media, and a virtual comminity. social networking sites, blogs, wikis, video sharing sites, hosted services, web applications, and mashups are all considered forms of web 2.0.

Exaples of current web 2.0 sites and old web 1.0 sites are:
Web 1.0 | Web 2.0
Ofoto > Flickr
mp3.com > Napster