Web 2.0

Web 2.0 is a trend in World Wide Web technology, and web design, a second generation of web-based communities and hosted services such as social-networking sites, wikis, and blogs, which aim to facilitate creativity information sharing, collaboration, and sharing among users. It is almost defined as the new era of the World Wide Web. The term became notable after the first O'Reilly Media Web 2.0 conference in 2004. Although the term suggests a new version of the World Wide Web, it does not refer to an update to any technical specifications, but to changes in the ways software developers and end-users use webs.

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 based on Ajax, Flex or similar rich media. The sites may also have social-networking aspects.

Examples:

Facebook (social-networking sites)
Facebook is a social networking website that was launched on February 4, 2004.
The free-access website allows users to join one or more networks, such as a school, place of employment, or geographic region to easily connect with other people in the same network.

Wikipedia (wikis)
Wikipedia is a free, multilingual, open content encyclopedia project operated by the non-profit Wikimedia Foundation.
Its name is a blend of the words wiki (a technology for creating collaborative websites) and encyclopedia. Launched in January 2001.
It is the largest, fastest-growing and most popular general reference work currently available on the Internet.

Blogger (blogs)
A blog (a portmanteau of web log) is a website where entries are commonly displayed in reverse chronological order.
Many blogs provide commentary or news on a particular subject; others function as more personal online diaries.
A typical blog combines text, images, and links to other blogs, web pages, and other media related to its topic. The ability for readers to leave comments in an interactive format is an important part of many blogs.