Web 2.0 is the name used to the describe the second generation of the world wide web, where it moved static HTML pages to a more interactive and dynamic web experience. Web 2.0 is focused on the ability for people to collaborate and share information online via social media, blogging and Web-based communities.
Web 2.0 signaled a change in which the world wide web became an interactive experience between users and Web publishers, rather than the one-way conversation that had previously existed. It also represents a more populist version of the Web, where new tools made it possible for nearly anyone to contribute, regardless of their technical knowledge.
Web 2.0 is pronounced web-two-point-o.
The meaning of the term Web 2.0 has evolved over time, but it has come include social media as a major component. Although community has always been a part of the web, new web applications such as AJAX and more modern browsers began providing opportunities for people to express themselves online as never before, and to combine applications to create a more integrated web. By 2005, the term Web 2.0 was well-established, and companies such as Google made huge strides to integrate information online. For example, a website that reviews restaurants may use social media, user-generated content, photographs from Flickr, Google maps, and content from around the web to create a more complete user experience.
To a certain extent, Web 2.0 is just an overused buzzword. On the other hand, there is a genuine difference between the brochure-ware websites in the early '90s versus the rich web apps of the modern web.