Looking at AJAX for the first time.

AJAX is a combination of technologies.

It requires client side scripting like javascript/DHTML but it also requires interaction with the web server, so you need your server side code like ASP.NET or PHP or the likes.

So there is definitely a connection with AJAX and server side languages like ASP.NET.

AJAX stands from asynchronous javascript and XML I think.

So what happens is you use javascript to submit an async HTTP request to the web server. The web server handles the request, in this case ASP.NET and sends a response back to the client. The client now uses javascript and DHTML to parse the response and can make the appropriate changes to the UI so the user does not need to post back the entire page so the experience is more dynamic.

Hello.

ASP.NET AJAX is the AJAX platform built by MS. It's well integrated with the ASP.NET paltform, but its client portion can be used on any page (it doesn't have to be an ASP.NET page). However, if you want to use all its features, you do need to built your app in ASP.NET

Do notice that there are several AJAX platforms out there...