Goat Simulator was made by Coffee Stains Studio, heavenly creators of the Sanctum franchise, on the Unreal physics engine. The game is about a female goat named Pilgor. She, along with other goats, are seemingly stupid and rock-brained, but they are secretly smart enough to have their own kingdom in Hell, where the Queen Goat resides, and THEIR OWN CULT BASED OFF OF THE EVIL GOAT QUEEN! Not many humans have taken notice of the goats, but when they do, it's usually just a light, "Aww!".
See the F.A.Q. for frequently asked questions.