Web 2.0 is the business revolution in the computer industry caused by the move to the Internet as a platform, and an attempt to understand the rules for success on that new platform.

Technology overview (from Wikipedia)

The sometimes complex and continually evolving technology infrastructure of Web 2.0 includes server-software,content-syndication, messaging-protacols, standards-oriented browsers with plugins and extentions, and various client-applications. The differing, yet complementary approaches of such elements provide Web 2.0 sites with information-storage, creation, and dissemination challenges and capabilities that go beyond what the public formerly expected in the environment of the so-called "Web 1.0".

Web 2.0 websites typically include some of the following features/techniques that Andrew McAfee used the acronym SLATES to refer to them:

1. “Search: the ease of finding information through keyword search which makes the platform valuable.
2. Links: guides to important pieces of information. The best pages are the most frequently linked to.
3. Authoring: the ability to create constantly updating content over a platform that is shifted from being the creation of a few to being the constantly updated, interlinked work. In wikis, the content is iterative in the sense that the people undo and redo each other's work. In blogs, content is cumulative in that posts and comments of individuals are accumulated over time.
4. Tags: categorization of content by creating tags that are simple, one-word descriptions to facilitate searching and avoid rigid, pre-made categories.
5. Extensions: automation some of the work and pattern matching by using algorithms e.g. amazon.com recommendations.
6. Signals: the use of RSS (Really Simple Syndication) technology to notify users with any changes of the content by sending e-mails to them.”