I am trying to learn backbone.js through the following example. Then I got stuck at the point ItemView = Backbone.View.extend

why you can use this.model.get? I thought this is referring to the instance of ItemView that would be created. Then why would ItemView has a model property at all?!!

    (function($){
      var Item = Backbone.Model.extend({
        defaults: {
          part1: 'hello',
          part2: 'world'
        }
      });

      var List = Backbone.Collection.extend({
        model: Item
      });


var ItemView = Backbone.View.extend({

        tagName: 'li', 
        initialize: function(){
          _.bindAll(this, 'render');
        },
        render: function(){
          $(this.el).html('<span>'+this.model.get('part1')+' '+this.model.get('part2')+'</span>');
          return this;
        }
      });

      var ListView = Backbone.View.extend({
        el: $('body'), 
        events: {
          'click button#add': 'addItem'
        },
        initialize: function(){
          _.bindAll(this, 'render', 'addItem', 'appendItem'); 

          this.collection = new List();
          this.collection.bind('add', this.appendItem); 

          this.counter = 0;
          this.render();
        },
        render: function(){
          $(this.el).append("<button id='add'>Add list item</button>");
          $(this.el).append("<ul></ul>");
          _(this.collection.models).each(function(item){ 
            appendItem(item);
          }, this);
        },
        addItem: function(){
          this.counter++;
          var item = new Item();
          item.set({
            part2: item.get('part2') + this.counter
          });
          this.collection.add(item);
        },

        appendItem: function(item){
          var itemView = new ItemView({
            model: item
          });
          $('ul', this.el).append(itemView.render().el);
        }
      });

      var listView = new ListView();      
    })(jQuery);