The term "Web 2.0" describes the changing trends in the use of World Wide Web technology and web design that aim to enhance creativity, communications, secure information sharing, collaboration and functionality of the web.

Web 2.0 concepts have led to the development and evolution of web culture communities and hosted services, such as social-networking sites, video sharing sites, wikis, blogs, and folksonomies.

The term first became notable after the 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 rather to changes in the ways software developers and end-users utilize the Web.

Web 2.0 encapsulates the idea of the proliferation of interconnectivity and interactivity of web-delivered content.

Tim O'Reilly regards Web 2.0 as the way that business embraces the strengths of the web and uses it as a platform. O'Reilly considers that Eric Schmidt's abridged slogan, don't fight the Internet, encompasses the essence of Web 2.0 - building applications and services around the unique features of the Internet, as opposed to expecting the Internet to suit as a platform (effectively "fighting the Internet").

In the opening talk of the first Web 2.0 conference, O'Reilly and John Battelle summarized what they saw as the themes of Web 2.0. They argued that the web had become a platform, with software above the level of a single device, leveraging the power of "The Long Tail," and with data as a driving force.

According to O'Reilly and Battelle, an architecture of participation where users can contribute website content creates network effects. Web 2.0 technologies tend to foster innovation in the assembly of systems and sites composed by pulling together features from distributed, independent developers. (This could be seen as a kind of "open source" or possible "Agile" development process, consistent with an end to the traditional software adoption cycle, typified by the so-called "perpetual beta".)

Web 2.0 technology encourages lightweight business models enabled by syndication of content and of service and by ease of picking-up by early adopters.