Web 2.0 is a term coined at a series of conferences by O'Reilly Media in 2004. The phrase suggests that a second generation of web communities has formed since the inception of the World Wide Web (or "Web 1.0"). Although Web 2.0 utilizes the same basic technology as the World Wide Web, the mode in which programmers and users alike view and interact with that technology has changed.
The key idea behind this change is that Web 2.0, unlike Web 1.0, emphasizes sharing within an online community through end user-driven content production, editing, and active participation. Whereas content in the days of Web 1.0 was produced under a top-down model of distribution (for example, a coder "hard-wiring" information via HTML onto a website for mass consumption), the vast majority of Web 2.0 content is user-generated and not (necessarily) strictly sanctioned by any distributing authority. Wikis (for example, Wikipedia), YouTube, blogs, and social networking sites (for example, Facebook and MySpace) are cornerstones of Web 2.0's new community-based ideal, in that they allow users to create or edit content quite easily; this encourages participation and intra-community communication.
Additionally, one of the core principles of this community-based ideal is that even if the majority of user-generated content is uninspired or even offensive, the ease of participation that Web 2.0 allows for permits a much greater volume of creativity. In summary, Web 2.0 could be described as a "social phenomenon embracing an approach to generating and distributing Web content itself, characterized by open communication, decentralization of authority, and the freedom to share and re-use".
One important technological factor that has allowed Web 2.0 to flourish is the widespread adoption of easy-to-use editing, content-generation, and open source platforms that shatter the "knowledge divide" of Web 1.0. Users must no longer be familiar with a coding language like Java or a formatting language like HTML in order to edit or generate content; intuitive platforms allow for ease of participation. For example, many blogs are written using the WordPress platform. Under this platform, users need not know HTML to contribute to the blog, and even more complicated functionalities (such as hyperlinking or special formatting) are possible through an intuitive graphical user interface (GUI). In terms of technical usability, Web 2.0 is an improvement over Web 1.0 in the same way that Windows or Mac OS was an improvement over the command-line computer interfaces of the 1970s and early 1980s. A second important technological factor is the the ubiquitous nature of the internet. By the end of 2008, an estimated 70 million households in the United States will have a broadband connection to the internet. In addition, public-use computers can be found in nearly every library across the United States. This high-speed network has allowed for a monumental shift from the basic hypertext based documents of the past to pages created with AJAX, Java, and Flash technologies--allowing for a more dynamic end-user experience. Additionally, these high-speed networks have allowed for rich multimedia. Sites such as YouTube and Facebook are rooted in these technologies as well as user created multimedia.