Ember.js - Index route vs. "top-level" resource route?

When creating a "standard" crud resource in Ember.js, what is the difference between the index route and the "main" route?

For example, a users resource:

// app.router.js

Router.map(function() {
    this.resource('users', function() {
      this.route('new);
      this.route('show', { path: '/:user_id'});
      this.route('edit', { path: '/:user_id/edit'});
    });
});

Which route should contain the following "main" model hook?

// app/routes/users/index.js OR app/routes/users.js?

export default Ember.Route.extend({
    model: function() {
        return this.store.find('user');
    }
});

In other words, should I use the UsersRoute or the UsersIndexRoute? I find this very confusing. Any help is greatly appreciated.