A corn or callus is a thickening of the outer layer of skin on your foot. Corns usually grow on top of the foot, often at a toe joint. Calluses spread on the bottom of the foot or on the outer edge of the heel or toe.
Symptoms: Corns can range from a slight thickening of skin to a painful, hard bump. They often form on top of buckled toe joints (hammer toes). If your toes curl under, corns may grow on the tips of the toes. You may also get a corn on the end of a toe if it rubs against your shoe. Corns can also grow between toes, often between the first and second toes.
A callus may spread across the ball of your foot. This type of callus is usually due to a problem with a metatarsal (long bone at the base of a toe, near the ball of the foot). A pinch callus may grow along the outer edge of the heel or the big toe. Some calluses press up into the foot instead of spreading on the outside. A callus may form a central core or plug of tissue where pressure is greatest.