Goat Simulator is all about causing as much destruction as you possibly can as a goat. It has been compared to an old-school skating game, except instead of being a skater, you're a goat, and instead of doing tricks, you wreck stuff.
Goat Simulator is a completely stupid game and, to be honest, you should probably spend your money on something else, such as a hula hoop, a pile of bricks, or maybe pool your money together with your friends and buy a real goat.