Learn AJAX in 5 mins
First I want to give credits to the author of the tutorial Learn AJAX in 20 mins that I improved to be less complicated and noob friendly 
AJAX stands for (as if you would remember it) Asynchronous JavaScript and XML. and it is used to send and receive data from the server without having to refresh the entire page.
I assume you have a basic knowledge of HTML and PHP.
Ad.
