So what is this AJAX thing?

What it is not is a bathroom scouring product - not in this context anyway. AJAX stands for Asynchronous JavaScript and XML, which is really quite meaningless and unhelpful to people who are not Geeks, so here is my, hopefully, simplified explanation.

Normally, when you click on a link on a web page that is intended to do something, the whole page is reloaded to achieve the desired result even if there is only a small part of the screen that needs to change. When using AJAX, if coded correctly, the main part of the sceen remains and only the desired piece is updated. The menu to the right is a good example. Each of the options links to a piece of AJAX code that changes the part of the screen and displays the new content. The result is a much quicker and pleasing experience for the person viewing the site.

Here is another, very simple, example: Click here...