What is the difference between using cur_frm and this.frm?

Hello;

What is the difference between using cur_frm and this.frm?
And when we do scripting in js file, what is this._super() is doing?
In other words: Why we use this? It indicates for what exactly?

Regards
Bilal

cur_frm is the global object for the current form and is deprecated in the new API.

Please specify which line are you talking about.

So, no more cur_frm in custom scripts? What about those who written earlier for custom apps and all?

@rmehta
Do you mean that this.fm is the alternative for cur_frm?

I see this._super() at sales_order.js file in this code:

erpnext.selling.SalesOrderController = erpnext.selling.SellingController.extend({
refresh: function(doc, dt, dn) {
var me = this;
this._super();

So what does it do?
Regards
Bilal