Ajax

From TheLinuxVault

AJAX stands for "Asynchronous JavaScript and XML"

Technically it refers to use of the JavaScript scripting language to exchange data with a server in XML formats and without needing to load everything at the same time, much of which may be redundant or already loaded.

To the rest of us, this means web pages which can be updated a bit at a time instead of all at once, which makes it quicker.