Some Examples:

1. Always – This method is called when the deferred object gets resolved or rejected
2. Done – This method is only called when the deferred object is gets resolved or succeded
3. Fail – This method is called when the deferred object is rejected or experienced an error
4. Then – a nice shorthand that allows you to pass in a done and then optionally a fail and a progress

Always

$.get( "www.yoursite.com/api" ).always(function() {
  console.log('this will run whether the $.get fails or succeeds');
});

Done

$.get( "www.yoursite.com/api" ).done(function() {
  console.log('this will run only when the $.get succeeds');
});

Fail

$.get( "www.yoursite.com/api" ).fail(function() {
  console.log('this will run if the $.get fails');
});

Then

$.get( "www.yoursite.com/api" ).then(
    function() {
      console.log('this run if the $.get succeeds');
    }, function() {
        console.log('this run if the $.get fails');
    }, function() {
        console.log('this run if the deferred generates a progress update');
    }
);