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 pages.
The AJAX technique makes Internet applications smaller, faster and more user-friendly.
Because the server returns a new page each time the user submits input, traditional web applications can run slowly and tend to be less user-friendly.
With an HTTP request, a web page can make a request to, and get a response from a web server - without reloading the page. The user will stay on the same page, and he or she will not notice that scripts request pages, or send data to a server in the background.
The XMLHttpRequest object is supported in Internet Explorer 5.0+, Safari 1.2, Mozilla 1.0 / Firefox, Opera 8+, and Netscape 7.
AJAX was made popular in 2005 by Google (with Google Suggest). Google Maps also uses AJAX.