Web 2.0 websites allow users to do more than just retrieve information: information sharing, interoperability, user-centered design and collaboration on the World Wide Web. Examples of Web 2.0 include web-based communities, hosted services, web applications, social-networking sites, video-sharing sites, wikis, blogs, mashups and folksonomies.

O'Reilly's Web 2.0 conferences have been held every year since 2004, attracting entrepreneurs, large companies, and technology reporters. In terms of the lay public, the term Web 2.0 was largely championed by bloggers and by technology journalists, culminating in the 2006 TIME magazine Person of The Year - "You." That is, TIME selected the masses of users who were participating in content creation on social networks, blogs, wikis, and media sharing sites.

Web 1.0 was about reading. Web 2.0 is about writing.

Web 1.0 was about companies. Web 2.0 is about communities.

Web 1.0 was about lectures. Web 2.0 is about conversation.

Web 1.0 was top-down.  Web 2.0 is bottom-up.

Web 1.0 was edited and produced.  Web 2.0 is raw.

Web 1.0 was text.  Web 2.0 is video.

Web 1.0 was professional. Web 2.0 is amature.

There are quite a lot of so called Web 2.0-services. You do not need to know them all ;-)

The Dutch ICT think tank EPN (recently merged with ECP.nl to ECP-EPN) has produced this short movie, clearifying one of the Web 3.0 concepts.