Calluses are toughened areas of skin that have become thick and hard as a response to repeated contact or pressure. Corns are specially shaped calluses that can be soft or hard, depending on the type of pressure and location on the foot. If you look at your own feet, the usual places you find calluses and corns are on the tops of your toes, the balls of the feet and the bottom surfaces of the foot and heels.
In the average person, as the three arches start to collapse and drop to the floor, the foot gets longer. This causes the toes to touch or rub on the end of the shoe. The increased pressure on the tops or bottoms of the toes and feet can then cause corns and calluses to form.