My friends asking me what is AJAX ? Football club from netherland ? Yes it is. But we are talking about AJAX in internet. I Search in google and found this result :

 A scripting technique for silently loading new data from the server. Although AJAX scripts commonly use the soon to be standardized XMLHttpRequest object, they could also use a hidden iframe or frame. An AJAX script is useless by itself. It also requires a DOM Scripting component to embed the received data in the document.

 the second result that i think really good explanation of AJAX is :

AJAX or Asynchronous JavaScript and XML is a term describing a web development technique for creating interactive web applications using a combination of: * HTML (or XHTML) and Cascading Style Sheets for presenting information* Document Object Model, JavaScript to dynamically display and interact with the information presented* XML, XSLT and the XMLHttpRequest object to interchange and manipulate data asynchronously with the web server (although AJAX applications can use other technologies …