UDK is a 3D engine, which means that it takes care of the boring parts of the programming for all the 3D graphics and physics and stuff, so that you can focus on what the game looks like and what happens in it (all the fun stuff).
UDK is completely free for personal use, and you can download it here: http://www.udk.com/download
I highly recommend the YouTube tutorials on how to use UDK by TheNewBoston: UDK Tutorials. They are very helpful, and rather entertaining.
I will be uploading some of my own videos of what I'm doing soon.
