title: Use of brackets in AngularJS
body: <p>My question might be stupid but I am having a hard time trying to determine whether use {} or {{}} or nothing in my HTML with AngularJS.</p>
  
  <p>I came accross the following :
    1/<code>ng-src = "{{ mysource }}"</code>
    2/ <code>ng-class = "{ active:tab===2 }"</code>
    3/ <code>ng-repeat = "foo in foos"</code></p>
  
  <p>I think I understand that 3/ is an instruction not a text replacement as in 1/ but why use simple brackets in 2/?</p>
  
  <p>Thanks a lot in advance for your help!</p>
  
  <p>Burger</p>