Beef steaks come from beef cattle.
Pork steaks come from pigs.
Lamb steaks come from sheep.
In all cases, the meat for steaks comes from the rear end of the animal. This is because the front legs of an animal do most of the hard work in moving the animal from place to place, and so fore-end meat tends to be tougher and needs longer, slower cooking to tenderise, while the hind legs just follow, and so hind-end meat is more tender and can be cooked more quickly.