You've heard of it. It is the latest buzz term for web programmers these days. AJAX is an acronym that stands for Asynchronous JavaScript and XML. AJAX gains its popularity by allowing data on a page to be dynamically updated without having to make the browser reload the page. I will describe more about how AJAX works, and then go into some sample code to try out.
This term has been made famous by some of Google's latest web apps. At the top of this list is Google Suggest, which gives you suggestions (go figure) on what you are searching for as you type based on popularity of the search term. If you aren't familiar with Google Suggest, check it out.