Don't understand 3rd argument to Backbone events binding
===

I'm reading up on how to use Backbone.js but it seems all the articles available online are all out of date compared to the latest version of the Backbone library? Which doesn't help!

I've seen for example an article by nettuts (first up in Google results) go into a discussion about using `Backbone.Controller` but that has been removed from Backbone so that was confusing to discover.

But regardless, my question is regarding the events object in Backbone. 

With a 'View' you can do...

    var ContactsView = Backbone.View.extend({
        initialize: function(){
            console.log('View initialized');
        },
        
        events: {
            'change select': 'displaySelected'
        },
        
        displaySelected: function (event) {
            console.log('get model data and display selected user', event);
        }
    });

...but you can't use the `events` property with a `Collection`, instead you need to use jQuery's bind method from within the `initialize` method...

    var Contacts = Backbone.Collection.extend({
        model: Contact,
        
        initialize: function(){
            this.bind('add', this.model_added, this);
        },
        
        model_added: function(){
            console.log('A new model has been created');
        }
    });

...first of all, why is this? 

But more importantly what is the 3rd argument `this` for? I looked up `bind` on the jQuery documentation (as there was no mention of `bind` on the Backbone site) and it doesn't have a 3rd argument?