Ember.JS: Ember-Objects and where they are exported to

I am trying to grasp the underlying system of Ember.JS. Whereto are those Ember-Objects exported and how are they used?

components:

export default Ember.Component.extend({ ... });

controllers:

export default Ember.Controller.extend({ ... });

models:

export default DS.Model.extend({ ... });

routes:

export default Ember.Route.extend({ ... });

... they all follow the same structure: they extend some object and export something.

Somebody knows more? Thanks!