define:Web 2.0 - Google Search
"Definitions of Web 2.0 on the Web:
* Web 2.0 is a term often applied to a perceived ongoing transition of the World Wide Web from a collection of websites to a full-fledged computing platform serving web applications to end users. Ultimately Web 2.0 services are expected to replace desktop computing applications for many purposes.
First I heard of it but Google is good!