what is render: function() ?

what is render: function() ?

Hello,

I am running a snippet of jquery that sends to the console the value of the current top of my page in the viewport.  
  1. render: function(data) {
  2. //Log the current scroll position.
  3. console.log(data.curTop);
  4. }

It works great and I understand the function, but what's with the  render: ? 

I tried to read about it but couldn't find what the render: is doing here, or maybe more specifically, what part of speech it is as it's not a jquery method, nor is it a variable or a function, per se.  So what is it and how is it working and what are its parameters?

Thanks!