Version 4.0 of the Unity platform is available for purchase and download today. This is important, because eventually every game not made with the Unreal Engine will be made with Unity. I am only exaggerating a little bit.
Unity is a cross-platform development engine that allows for developers to develop a game on one platform and then deploy it anywhere—smartphone, PC, Facebook, tablets, particularly technologically advanced house plants—anywhere. It's a key player in the movement to create platform-free games. Games like Panglore's Knightly Adventure. Not just ports, but the same game running everywhere. It's the future.