title: what does the "on" and "emit" function for?
body: <p>I am a newbie in Nodejs and I actually don't still understand the mission of two method : "on" and "emit" in socket.io</p>
  
  <p>Sorry  .Let me guess:</p>
  
  <ul>
  <li><p>"on" method is listen from client/server</p></li>
  <li><p>"emit" to broadcast a event to client/server</p></li>
  </ul>
  
  <p>And questions are :</p>
  
  <p>1.Can we create a custom event beside built-in events ?</p>
  
  <p>What does socket.io apply for ?</p>