Web 2.0 at a glance

Lets make sure you're crystal clear on this idea of the Web 2.0. When you hear the term Web 2.0, you should first ask, "What's Web 1.0?" Although you'll rarely hear Web 1.0, it is meant to refer to the traditional Web where you have a very distinct request and response model. For example, go to Amazon.com and click a button or enter a search term. A request is made to a server and then a response comes back to your browser. That request has a lot more than just a list of books and titles, though; it's actually another complete HTML page. As a result, you probably get some flashing or flickering as your Web browser's screen is redrawn with this new HTML page. In fact, you can clearly see the request and response, delineated by each new page you see.

The Web 2.0 dispenses with this very visible back-and-forth (to a large degree). As an example, visit a site like Google Maps or Flickr. On Google Maps, for example, you can drag the map around and zoom in and zoom out with very little redrawing. Of course, requests and responses do go on here, but all behind the scenes. As a user, the experience is much more pleasant and feels a lot like a desktop application. This new feel and paradigm is what you see when someone refers to Web 2.0. - Article source