Web 2.0 per “Definition” and per “Opinion”

Web 2.0, a phrase coined by O’Reilly Media in 2004, refers to a supposed second-generation of Internet-based services — such as social networking sites, wikis, communication tools, and folksonomies — that let people collaborate and share information online in previously unavailable ways. O’Reilly Media, in collaboration with MediaLive International, used the phrase as a title for a series of conferences and since then it has become a popular (though ill-defined and often criticized) buzzword amongst certain technical and marketing communities. This is a nice well done Wikipedia entry that will give you a good idea what Web 2.0 stands for.