Web 2.0 refers to:
… web applications that facilitate interactive information sharing, interoperability, user-centred design, and collaboration on the World Wide Web. A Web 2.0 site gives its users the free choice to interact or collaborate with each other in a social media dialogue as creators of user-generated content in a virtual community, in contrast to websites where users (consumers) are limited to the passive viewing of content that was created for them. Examples of Web 2.0 include social-networking sites, blogs, wikis, video-sharing sites, hosted services, web applications … (Wikipedia, 2010).
The term ‘Web 2.0’ can be traced back to Tom O’Reilly and the O’Reilly Media Conference in 2004.