Ajax is a fairly recently coined term describing a Web application that updates portions of a given Web page without refreshing the entire page. Java Script must be Enabled through the Internet Browser for this type of application to work.
I personally enjoy coding Web applications which dynamically update Blogs, HTML, RSS Feeds and Ticker type informational displays with XML data. The following Ticker Message line reads from the Howes-IT-Going Web Page Ticker (ticker.xml) and then refreshes only the text display line below. You can view the source code of this web page to see how it is done.
As computer users(people surfing the web) become more and more sophisticated, they look for more responsive and dynamic web applications. There is still a gap between the user interface (UI) of a Web application and what can be attained with a traditional Web application.
Web sites like Google Maps or Google Suggest provide an exceptional level of user interaction as maps are zoomed and scrolled or as search terms are suggested to the user as characters are typed into a search box. Google has been one of the big adopters of Ajax as they strive to provide a new level of user interaction.
An Ajax Web application can be easier for a user to work with because it follows a more familiar UI. Developers utilizing Ajax should be careful that their applications do not confuse or distract a user which could hinder web page navigation.
There are several drawbacks to the fetch and display approach. First of all, much of the content in an HTML document is redundant. Less load is placed on servers if most of a page remains static and only the different content changes.
Your browser already does a good job of caching content such as images and external style and script files, but transferring less data makes pages load faster.
Secondly, an Ajax Web application will change page data quicker than its traditional counterpart. Since less data is transferred, it can be loaded more quickly. The response time of an Ajax Web application can be nearly as fast as that for a desktop application.