title: Controller in Backbone.js
body: <p>I'm new to Backbone.js. I have gone through the documentation. My question is
   where does the controller concept come into picture? In other words, what is a controller in Backbone.js?</p>
  
  <p>I heard that the router is the controller. If so, why it is considered as a controller? Can we develop simple basic apps without the Router also? In that case what will be the controller?</p>