Q:

Why AJAX has called Asynchronous? Can you please describe any one please?

I have some doubt in Asynchronous and synchronous terms in ajax.
How Asynchronous process will work?
Can you please let us know about this terms?

A:

Synchronous ( async: false ) – Script stops and waits for the server to send back a reply before continuing. 
Asynchronous ( async: true ) – Async requests occur on a background thread, meaning that the UI is not going to be blocked while the request is processing.

Why AJAX has called Asynchronous? Can you please describe any one
  please?

asynchronous is the best because the client and the server run independently of each other for the duration of the function call.
During a normal function call, you make the call, and the calling function doesn't get to execute again until the function call finishes and returns. The caller and the callee are always synchronized.
During an asynchronous function call, you make the call, and then control returns immediately to the caller. The callee then returns a value some indeterminate amount of time later. That "indeterminate amount of time" means the caller and callee are no longer synchronized, so it's asynchronous.
Meanwhile you can make multiple request if you set async:true because control returns immediately, it will not wait like synchronous call till it receives response from server, here is picture which give clear idea.

