Defining Web 2.0

In alluding to the version-numbers that commonly designate software upgrades, the phrase "Web 2.0" may hint at an improved form of the World Wide Web. Advocates of the concept suggest that technologies such as weblogs, social bookmarking, wikis, podcasts, RSS feeds (and other forms of many-to-many publishing), social software, Web APIs, Web standards and online Web services imply a significant change in web usage. Stephen Fry (actor, author and broadcaster) describes Web 2.0 as "an idea in people’s heads rather than a reality. It’s actually an idea that the reciprocity between the user and the provider is what’s emphasized. In other words, genuine interactivity if you like, simply because people can upload as well as download" .

Source frorm : http://en.wikipedia.org