var CommentModel = ...

var CommentsCollection = Backbone.Collection.extend({...});

var commentTemplate = _.template('...');

var CommentView = Backbone.View.extend({...});

var CommentsApp = Backbone.View.extend({

  el: $('.comments'),

  initialize: function(){
    this.collection = new CommentsCollection();
    this.listenTo( this.collection, 'add', this.renderComment );
    this.listenTo( this.collection, 'remove', this.renderCommentCount );
  },

  renderComment: function(model){
    model.view = new CommentView({ model: model });
    var comment = model.view.render();
    this.$('#comment-list').prepend( comment );
    this.resetFormFields();
    this.renderCommentCount();
  },

  resetFormFields: function(){...
  },

  renderCommentCount: function(){... },

  events: {
    'submit form': 'createComment'
  },

  createComment: function(event){
    event.preventDefault();

    // Create a new Comment Model with the data in the form
    var comment = {
      content: this.$('form textarea').val(),
      email: this.$('form input[name="email"]').val(),
      created_at: +new Date()
    };
    // The `validate` option ensures that empty comments aren't added
    this.collection.add( comment, { validate: true });
  }

});

$(function(){
  window.comments = new CommentsApp();
});

Line #15. : The  ​add​ event listener. When a model has succesfully been added to the collection, this event fires. This is a general structure of a backbone app.Some things are still missing (persistance, editing notes, authentication). We’ll see how to use AMD modules, Mozilla Persona etc.