AJAX is the use of the XMLHttpRequest object in JavaScript to load new content from a server into a page, without reloading the page. A good example of this is Twitter. Type your new message into the box, press the button, and your message is sent to the server (and a response is sent back) without the page being reloaded. This is AJAX.

What AJAX isn’t, but people keep referring to as AJAX, is dynamic Javascript tricks such as Script.aculo.us effects.

Please use the term “AJAX” to refer to asynchronous HTTP requests, and not any old bit of JavaScript. We already have a term for that, it’s “DHTML,” or “Dynamic HTML.”