简单的示例AJAX Web应用程序，包括客户端和服务器方面

I am trying to learn AJAX, and I am referring to online material and some books. I came to know that AJAX isn't a new technology as such, however, it is a way of using existing technologies for "faster" web-applications (or changing some part of the web-page without refreshing the whole page).I am trying to learn AJAX, and I am referring t