Does the application route load automatically and load the application.hbs in an Ember app?

I have this as my router.js. Note that it has no application route:

import Ember from 'ember';
import config from './config/environment';

var Router = Ember.Router.extend({
  location: config.locationType
});

Router.map(function() {
  this.route('todos', { path: '/'});
});

export default Router;

When I hit the home path, I see my application.hbs template and the todos.hbs template is loaded in the outlet. This is my application.hbs:

<section id="todoapp">
  <header id="header">
    <h1>todos header in application.hbs</h1>
  </header>

  {{outlet}}
</section>

<footer id="info">
  <p>
    Footer in application.hbs. Double-click to edit a todo
  </p>
</footer>

Why does my application.hbs get loaded?

I assume Ember knows to also load the todos.js in my routes folder which is this:

import Ember from 'ember';

export default Ember.Route.extend({
  model() {
    let todos = [
      {
        title: 'Learn Ember',
        complete: false,
      },
      {
        title: 'Solve World Hunger',
        complete: false,
      }
    ];
    return todos;
  }
});

And this is my todos.hbs template:

<h2>Todos Template</h2>

<ul>
    {{#each model as |todo|}}
        <li>
            {{todo.title}}
        </li>
    {{/each}}
</ul>

Main questions
1. Why does my application.hbs get loaded when I hit the home route?
2. What is export default mean?
3. What is the line import Ember from 'ember' doing? Where is 'ember' coming from?