http://blog.jquery.com/2011/01/31/jquery-15-released/ ajax rewrite: a call to jQuery.ajax (or jQuery.get, jQuery.post, etc.) now returns a jqXHR object that provides consistency to the XMLHttpRequest object across platforms much more extensible – allowing you to attach all sort of data handlers, filters, and transports.
deferred objects: to work with return values that may not be immediately present (such as the return result from an asynchronous Ajax request).