What is Web 2.0??

Many people like me have heard about Web 2.0 somewhere but not really know what it actually is? Is it a new web programming language or a version number of a program?
I got to know more about it after a recent seminar on Web security.

Web 2.0 is actual a concept that uses Internet technology and Web design to enhance creativity, information sharing and collaboration among users.
Web 2.0 technologies enable Web architectures greater access to data and functions. Web 2.0 applications should not be understood as a new technology, but a new use of old technologies.

Web 2.0 websites allow users to do more than just retrieve information. They can build on the interactive facilities of "Web 1.0" to provide "Network as platform" computing, allowing users to run software-applications entirely through a browser. Users can own the data on a Web 2.0 site and exercise control over that data. These sites may have an "Architecture of participation" that encourages users to add value to the application as they use it. This stands in contrast to very old traditional websites, the sort which limited visitors to viewing and whose content only the site's owner could modify. Web 2.0 sites often feature a rich, user-friendly interface.

Some misconception that Web 2.0 is AJAX because many Web 2.0 sites rely heavily on AJAX. But there are many technologies that supports Web 2.0, to list afew:
- AJAX (Asynchonous Javascript and XML)
- XML (eXtensible Markup Language)
- JSON (JavaScript Object Notation)
- SOAP (Simple Object Access Protocol)
- WSDL (Web Services Description Language)
- RSS/Atom feeds
- Flash, ActiveX

Web 2.0 have led to the development and evolution of web-based communities and hosted services, such as Google, Linkin, MySpace to name afew.