As the web grows and bandwidth increases, people demand more from their online experiences. They want more content and graphics, smarter applications, and instantaneous responses. Until recently, web application developers -- and end users for that matter -- struggled with slow, unresponsive systems where entire pages had to be reloaded to update a single element. The web's architecture simply was not a convenient platform for demanding applications. Many solutions, like Google Maps, were not even possible until the wide-spread adoption of Ajax occurred.

What is Ajax? Ajax is an aceronym for Asynchronous Javascript + XML. It's a term created by Adaptive Path describing a collection of standard web technologies that, when combined, provide a more seamless experience for web application users.

The XMLHttpRequest object is the key component to Ajax that makes it so useful. It provides a mechanism for the client (through Javascript) to send information to the server and receive a response as XML. The response XML can be processed in the background and used to dynamically update elements on the page without ever signaling to the user that a new request was made. In effect, information flows, and screens are updated, more like in desktop applications than in old-fashioned web applications.