The term Web 2.0 was coined by O'Reilly Media, a technology publishing powerhouse, founded by Tim O'Reilly. Web 2.0 and AJAX are often considered synonymous. However, AJAX excited before the Web 2.0 term was coined by O'Reilly. Before we attempt to explain in simple terms what Web 2.0 really means, let us define the primary players in the Web scene: users (you, me, and everyone else), publishers (companies and organizations that provided the contents). We can classify the evolution of Web as follows into two pseudo versions.

In the early days of the Web, users mostly browsed Web sites to read what is already published by the content publishers. There were hardly any influence or input from the users that affected the contents on the Web sites. Web was simply the new digital magazine or newspaper.

With the advances of client-side technologies: JavaScript, Flash and Web browsers like Firefox, the next phase of Web evolution started with the theme being "User-generated contents". Now the user has ability to write on the Web. Users started using the Web as an active medium by writing blogs, posting audio/video, creating Web pages, forming social networks, creating meshups using RSS feeds, linking services with widgets, etc.