title: What do parenthesis after curly braces mean?
body: <p>I have seen Javascript code that uses parenthesis immediately after a function's closing curly brace, I can't understand what they're used for. </p>
  
  <p>Example:</p>
  
  <pre><code>function foo(bar){
    return bar;
  }(0);
  </code></pre>
  
  <ul>
  <li><p>What does <code>(0)</code> do?</p></li>
  <li><p>What is this called?</p></li>
  <li><p>When should you use this technique?</p></li>
  </ul>