From http://www.w3schools.com (Copyright Refsnes Data)

AJAX Introduction

AJAX stands for Asynchronous JavaScript And XML.

What You Should Already Know

Before you continue you should have a basic understanding of the following:

HTML / XHTML
JavaScript

If you want to study these subjects first, find the tutorials on our Home page.

AJAX = Asynchronous JavaScript and XML

AJAX is not a new programming language, but a technique for creating better, faster, and more interactive web applications.

With AJAX, your JavaScript can communicate directly with the server, using the JavaScript XMLHttpRequest object. With this object, your JavaScript can trade data with a web server, without reloading the page.

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.

AJAX is a browser technology independent of web server software.

AJAX is Based on Web Standards

AJAX is based on the following web standards:

JavaScript
XML
HTML
CSS

The web standards used in AJAX are well defined, and supported by all major browsers. AJAX applications are browser and platform independent.

AJAX is About Better Internet Applications

Web applications have many benefits over desktop applications; they can reach a larger audience, they are easier to install and support, and easier to develop.

However, Internet applications are not always as "rich" and user-friendly as traditional desktop applications.

With AJAX, Internet applications can be made richer and more user-friendly.

You Can Start Using AJAX Today

There is nothing new to learn.

AJAX is based on existing standards. These standards have been used by most developers for several years.