title: What is the difference between ngAfterViewInit() and ngAfterViewChecked()?
body: <p>I am learning Angular 2. In the angular 2 lifecycle hooks </p>
  
  <pre><code>ngAfterContentInit -- Component content has been initialized
  ngAfterContentChecked -- Component content has been Checked
  ngAfterViewInit -- Component views are initialized
  ngAfterViewChecked -- Component views have been checked
  </code></pre>
  
  <p>I can't understand the difference between the ngAfterContentInit Vs ngAfterContentChecked, ngAfterViewInit Vs ngAfterViewChecked.</p>
  
  <p>They mentioned <strong>Component content has been Checked</strong> and <strong>Component views have been checked</strong>.  I can't understand what that word "Checked" mentioned?</p>
  
  <p>Can any one explain.</p>