AJAX is a web development technique for creating interactive web applications. If you know JavaScript, HTML, CSS, and XML, then you need to spend just one hour to start with AJAX.AJAX, short for Asynchronous JavaScript And XML, allows you to load data in the background and display it on your webpage, without refreshing the page. This allows you to create websites with much richer functionality. Popular web applications like Gmail, Outlook Web Access, and Google Maps uses AJAX extensively, to provide you with a more responsive, desktop-like experience.
Using AJAX can be a bit cumbersome, because the various browsers have different implementations to support AJAX. Normally this would force you to write code to respond differently, depending on the browser, but fortunately, jQuery has done this for us, which allows us to write AJAX functionality with as little as a single line of code.
You should be aware of the fact that thre are both advantages and disadvantages to using AJAX on your page though, which means that you should always consider carefully before deciding to use it instead of doing a regular postback to the server. Here's a summary: