What is Web 2.0?

Web 2.0, a phrase coined by O'Reilly Media in 2003 and popularized by the first Web 2.0 conference in 2004, refers to a perceived second-generation of Web based communities and hosted services such as social networking sites, wikis and folksonomies that facilitate collaboration and sharing between users. O'Reilly Media titled a series of conferences around the phrase, and it has since become widely adopted.

Introduction
Time bar of Web 2.0 buzz words. This image shows the age of some buzzwords sometimes used in Web 2.0 lingo and its dependencies. By alluding to the version-numbers that commonly designate software upgrades, the phrase "Web 2.0" hints at an improved form of the World Wide Web; advocates suggest that technologies such as weblogs, social bookmarking, wikis, podcasts, RSS feeds (and other forms of many-to-many publishing), social software, Web APIs, Web standards and online Web services imply a significant change in web usage.

As used by its supporters, the phrase "Web 2.0" can also refer to one or more of the following:

1. The transition of web sites from isolated information silos to sources of content and functionality, thus becoming computing platforms serving web applications to end-users
2. A social phenomenon embracing an approach to generating and distributing Web content itself, characterized by open communication, decentralization of authority, freedom to share and re-use, and "the market as a conversation"
3. Enhanced organization and categorization of content, emphasizing deep linking
4. A rise in the economic value of the Web, possibly surpassing the impact of the dot-com boom of the late 1990s.

Characteristics
This section overlaps with other sections; it should be combined with the rest of the article.Please post any comments on this issue on the talk page. While interested parties continue to debate the definition of a Web 2.0 application, a Web 2.0 web-site may exhibit some basic common characteristics.

These might include:

1. "Network as platform" — delivering (and allowing users to use) applications entirely through a browser.
2. Users owning the data on the site and exercising control over the data.
3. An architecture of participation that encourages users to add value to the application as they use it. This stands in sharp contrast to hierarchical access-control in applications, in which systems categorize users into roles with varying levels of functionality.
4. A rich, interactive, user-friendly interface based on Ajax or similar frameworks.
5. Some social-networking aspects.
6. Enhanced graphical interfaces such as gradients and rounded corners (absent in the so-called Web 1.0 era).