what is this Ajax

Now-a-days we hear a lot about Ajax everywhere. Some say its WEB2.0 jargon. Let us see what Ajax is ..? AJAX is an acronym for Asynchronous JavaScript And XML.

How is AJAX useful..?
With AJAX one can create better, faster, and more user friendly web applications. It is based on JavaScript and HTTP requests.

How does it work..?
AJAX uses JavaScript to send and receive data between a web browser and a web server.
The AJAX technique makes web pages more responsive by exchanging data with the web server behind the scenes, instead of reloading an entire web page each time a user makes a change.

AJAX uses asynchronous data transfer (HTTP requests) between the browser and the web server, allowing web pages to request small bits of information from the server instead of whole page getting submitted at once.

AJAX is more of Browser oriented technology ... and it does not depend on web server used.

Traditional way and AJAX way...
Earlier, the user have to click 'Submit' button to send/get information from the server and wait till the new page loads back. Developer used the HTML form and GET or POST methods to retrieve data from the server.

Since the server needed to send a new page each time the user submits, web apps were very slow. But with Ajax way, javascripts communicates directly with the server, through the XMLHttpRequest object. There need of reloading the page is not there, these scripts requests or sends data to the server in the background.