Callouses are layers of thickened hard dead skin that occur over bony prominences, usually on the soles of the feet and knuckles of the toes. As the thickened skin hardens a burning sensation may be felt making it uncomfortable to walk.
Corns are either hard or soft. Hard corns are dense, concentrated areas of thick hard skin which pushes back into the foot and feels like a stone sticking into your foot. Soft corns occur between the toes and develop due to moisture and friction. Corns can be very painful, affecting mobility and balance.
Both callouses and corns are caused by friction. They occur more frequently as a person ages due to the reduction of the fatty pad on the sole of the foot, causing the bones to become more prominent.