Answer:
The "hoof" is the foot of the horse. It is the part at the end of the leg that comes in contact with the ground. In prehistoric times the ancestors of the horse had toes almost like a dog, but over evoultion the middle toe lenghtened and strengthened, while the other toes receded. The modern horse has his middle toe as his hoof (foot), and the reminants of the other toes can be seen further up the leg, now called chestnuts, and sometimes at the back of the fetlock.