A callus is a section of dead skin that has thickened over time due to repetitive friction or rubbing. They usually occur on the feet, as this is typically the source of most pressure and friction, but they can also occur on other parts of the body, such as the elbows, hands and knees. There are even action-specific calluses, such as those developed by violin players on their chin.
Calluses are usually yellowish or pale in colour and feel lumpy. However, because they consist of dead skin, they are usually less sensitive than other areas of skin. They are usually bigger than corns, with less defined edges, and typically form on bony edges where rubbing occurs, such as the areas around the toes, on the heels or the fingers.