Web 2.0" refers to web development and web design that facilitates interactive 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. A Web 2.0 site allows its users to interact with other users or to change website content, in contrast to non-interactive websites where users are limited to the passive viewing of information that is provided to them.
Web 2.0 websites typically include some of the following features/techniques
The ease of finding information through keyword search.
Ad-hoc guides to other relevant information.
The ability to create constantly updating content over a platform that is shifted from being the creation of a few to being constantly updated, interlinked work. In wikis, the content is iterative in the sense that users undo and redo each other's work. In blogs, content is cumulative in that posts and comments of individuals are accumulated over time.
Categorization of content by creating tags: simple, one-word user-determined descriptions to facilitate searching and avoid rigid, pre-made categories.
Powerful algorithms that leverage the Web as an application platform as well as a document server.
The use of RSS technology to rapidly notify users of content changes.