[jQuery] $.ajaxSuccess.

Sorry about my grammar,
English isn't my tang.
What is the different betwen:
$(document).ajaxSucess(function () {})
$('div').ajaxSucess(function () {})
$.ajaxSetup (success: function () {} )
*When I am execute*
$.ajax(url);
Also, how I can change the data before it's send to the server by
using beforeSubmit?
Thank you.