AJAX:

AJAX stands for Asynchronous JavaScript And XML. AJAX is a type of programming made popular in 2005 by Google (with Google Suggest). AJAX is not a new programming language, but a new way to use existing standards. With AJAX you can create better, faster, and more user-friendly web applications. AJAX is based on JavaScript and HTTP requests.
AJAX, is a group of interrelated web development techniques used for creating interactive web applications or rich Internet applications. With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page.
Advantages
• In many cases, the pages on a website consist of much content that is common between them. Using traditional methods, that content would have to be reloaded on every request. However, using Ajax, a web application can request only the content that needs to be updated, thus drastically reducing bandwidth usage and load time.
• The use of asynchronous requests allows the client's Web browser UI to be more interactive and to respond quickly to inputs, and sections of pages can also be reloaded individually. Users may perceive the application to be faster or more responsive, even if the application has not changed on the server side.
• The use of Ajax can reduce connections to the server, since scripts and style sheets only have to be requested once.