A callus is a thickened area of skin that forms in response to repeated friction, pressure, or irritation. It typically develops on the hands and feet, where the skin is more exposed to stress. Calluses serve as a protective barrier, helping to prevent blisters and other injuries. Calluses can vary in size and texture, often appearing yellowish or gray. While they are generally harmless, excessive callus formation can lead to discomfort or pain. Proper foot care, including wearing well-fitting shoes and using moisturizers, can help manage and prevent calluses from becoming problematic.