What is the use of colons in this examples

What is the use of colons in this examples

I have noticed the usages of colons in jquery for instance

  1. config: {
  2.             duration: 400,
  3.             easing: 'swing',
  4.             callback: undefined,
  5.             durationMode: 'each',
  6.             offsetTop: 0,
  7.             offsetLeft: 0
  8.         },
and  
  1. $('#table').animate({
  2.             scrollTop: $('#table').scrollTop() + 100
            });
I have seen colons being used in javascript like 

  1. var o = { r: 'some value', t: 'some other value' };

What do the colon in jquery mean?.