AJAX, what is this anyway?

What is AJAX?

Ajax, shorthand for Asynchronous JavaScript and XML, is a web development technique for creating interactive web applications. The intent is to make web pages feel more responsive by exchanging small amounts of data with the server behind the scenes, so that the entire web page does not have to be reloaded each time the user makes a change. This is meant to increase the web page's interactivity, speed, and usability.

The Ajax technique uses a combination of:

XHTML (or HTML) and CSS, for marking up and styling information.
The DOM accessed with a client-side scripting language, especially ECMAScript implementations such as JavaScript and JScript, to dynamically display and interact with the information presented.
The XMLHttpRequest object to exchange data asynchronously with the web server. In some Ajax frameworks and in certain situations, an IFrame object is used instead of the XMLHttpRequest object to exchange data with the web server.

And optionally:

XML is sometimes used as the format for transferring data between the server and client, although any format will work, including preformatted HTML, plain text, JSON and even EBML. These files may be created dynamically by some form of server-side scripting.
SOAP is a protocol for exchanging XML-based messages over a computer network, normally using HTTP. SOAP forms the foundation layer of the Web services stack, providing a basic messaging framework that more abstract layers can build on.