title: Which is better .success() or .then() in angular
body: <p>I am making an ajax call to server to fetch some data.</p>
  
  <pre><code>$.ajax(
  {
  url: "myserver",
  method: "GET",
  }.success(function(data)
  { }
  .error(function(e)
  { }
  )
  </code></pre>
  
  <p>I have been reading about <strong>.then()</strong>. </p>
  
  <p>Is there any performance benefit of using .then() over .success()?</p>
  
  <p>Is there any particular scenario where I should use .then()  and .success()?</p>
  
  <p>Plus, whoever answers,please brief me in short What is Promises.</p>