Web 2.0 is a term originally coined by Tim O'Reilly to describe what many see as a new trends in Web design, development, and usage, and an accompanying commercial and cultural 'rebirth' of the Web from the "dot com" bust. O'Reilly described Web 2.0 as the business shift that arises from the rise of the "Internet as platform" (much as, in the technology industry, operating systems and application software before would go to make a platform).
The characteristics of 'Web 2.0' platforms include some kind of participatory component ('social software' was a phrase used to describe software that improved functionality and usefulness as more people used it), ubiquity (with services being offered both through a web browser and on other websites through widgets, on the desktop, on mobile devices, and through large numbers of partner channels), remixability (data and content from multiple services and sources being 'mashed-up'), utilisation of social networking, collective intelligence, and the idea of hosting applications and services in the 'cloud' rather than on servers that a person owns.
A principle characteristic of Web 2.0 applications is utilization of users (readers, consumers) as content producers. These applications include Google (where users can comment and alter the placement of search results), blogs (where readers can comment on postings), Technorati (user-generated filtering), Wikis (such as The Citizendium), Digg, Diigo, and other bookmarking services (user-generated tagging), MySpace, FaceBook and Twitter (user-generated social networking), and YouTube (user-generated video).