How does import statements work in ember-cli?

Am quite new to emberjs and ember-cli.

And I have always been wondering how a statement like this works:

import Ember from 'ember'

Does 'ember build' look up for 'ember' in node_modules?

I understand statements like this with relative paths:

import ENV from './config/environment'

but not the ones referred without a path.

This question raises in connection with Could not find module ember-validations, in an effort to find its root cause.