title: what does # (hash) do in angular2
body: <p>I am new to angular2 . I want to know what does # (hash) do in angular2. 
  e.g </p>
  
  <pre><code> &lt;ion-card #mycards1 swing-card *ngFor="let group of groups"&gt;
  </code></pre>
  
  <p>and this </p>
  
  <pre><code>       &lt;ul&gt;
            &lt;li
            *ngFor="#Item of Items"
            (click)="onItemClicked(Item)"&gt;
                {{ Item.name }}
            &lt;/li&gt;
         &lt;/ul&gt;
  </code></pre>