Corns are areas of thick, hardened, dead skin. They form to protect the skin and structures under the skin from pressure, friction, and injury. A corn may have a yellow ring with a grey centre. Or it may look darker than the nearby skin. It may feel bumpy. And it may hurt or be less sensitive to the touch than the surrounding skin.

Corns are usually found where toes rub together. A soft corn is found between toes (usually between the fourth and fifth toes), while a hard corn is often found over a bony part of a toe (usually on the fifth toe).