Ember: What exactly the chain of modelFor and get do at Route?

I am in Route. What exactly the chain of modelFor and get do the job ?

Syntax:

 import Ember from "ember";

var PagesRoute = Ember.Route.extend({
    model: function(){
        return this.modelFor('campaign').get('pages'); # what exactly it is doing here ?
    }
});
export default PagesRoute;

BTW, what is the best way to debug step by step code?