Corns generally occur on the tops and sides of the toes. A hard corn is a small patch of thickened, dead skin with a packed center. A soft corn has a much thinner surface and usually occurs between the 4th and 5th toes. A seed corn is a tiny, discrete callous that can be very tender if it's on a weight-bearing part of the foot. Seed corns tend to occur on the bottom of the feet, and some doctors believe this condition is caused by plugged sweat ducts.
Calluses can develop on hands, feet, or anywhere there is repeated friction -- even on a violinist's chin. Like corns, calluses have several variants. The common callus usually occurs when there's been a lot of rubbing against the hands or feet. A plantar callus is found on the bottom of the foot. Read more about corns and calluses - symptoms, treatments and prevention.
Slideshow: Pictures of Common Foot Problems