A blend of well-known technologies and a nifty JavaScript tool form the basis of a snappier and more powerful application model for the Web. If you're afraid of acronym overload, don't worrythis one's easy. It's called Ajax, which stands for Asynchronous JavaScript and XML.
Remember when users called the Internet the "world wide wait?" Way back in the Neolithic era of the Web? With some applications, that aspect of the Web hasn't really changed that much: fill out form, click button, web page goes away, wait, page refreshes, correct mistake, click, wait, wait... You've been stuck in this limbo before.