title: Yii2: uniqueID and id modules properties
body: <p><a href="http://www.yiiframework.com/doc-2.0/yii-base-module.html" rel="nofollow">Class yii\base\Module</a> has 2 properties: <em>id</em> and <em>uniqueId</em>. The former "uniquely identifies this module among other modules which have the same parent", while the latter - just unique id. But I still don't understand the diff. Why need we <em>id</em> to identify module, especially from modules with the same parent, if there is <em>uniqueId</em>, that identifies module too? It would be nice to show me example, which reveals the need for both these properies.</p>