The much disputed term, Web 2.0, refers to a trend in websites towards greater collaboration, user input and shared information. Web 2.0-style sites are typically blogs, social networks, or wikis. They often use technologies like RSS and Ajax and involve user generated content and tagging.

Although there are many elements that are considered part of the Web 2.0 movement, the main feature that distinguishes Web 2.0 sites from other sites is that they would not function well or at all without being fueled by the mass of users connected to the Internet. In other words, they could not be used as effectively run alone on a home computer.

Web 1.0 websites are a one way affair. The creator of the site publishes the content, the users of the site consume it. Web 2.0 blurs the line between creator and user, making a truly collaborative two-way experience for all involved.

An encyclopedia program could easily be used to find information on a desktop PC without the Internet, but Wikipedia requires the constant input of users to generate material, and without that it could not exist in anything like its present form. Sears.com could be run as effectively as a mail order business (and has been). But sites like Amazon.com and eBay that heavily incorporate user ratings, user reviews, and a marketplace where users can sell as well as buy, would be crippled offline.

1. "Web 2.0 is social, it’s open (or at least it should be), it’s letting go of control over your data, it’s mixing the global with the local."—Richard MacManus
2. "Web 2.0 is a marketing concept used by venture capitalists and conference promoters to try to call another bubble into existence."—Dave Winer
3. "I think Web 2.0 is of course a piece of jargon, nobody even knows what it means."—Tim Berners-Lee
4. "If an essential part of Web 2.0 is harnessing collective intelligence, turning the web into a kind of global brain, the blogosphere is the equivalent of constant mental chatter in the forebrain, the voice we hear in all of our heads. It may not reflect the deep structure of the brain, which is often unconscious, but is instead the equivalent of conscious thought." —Tim O'Reilly
5. "Web 2.0 is about people"—David Sifry