Plantar warts are small growths of the skin that usually appear on the heels or other weight-bearing areas of your feet. This pressure of your body causes plantar warts to grow inward beneath a hard, thick layer of skin (callus), often causing pain
Besides plantar warts, there are also palmar warts that grow on the skin of your hands.
Plantar and palmar warts are both caused by a virus called HPV. The virus can spread indirectly from person to person and loves warm moist environments, such as showers. The risk of getting the virus may increase if you have cuts or breaks in the skin or if you have a weakened immune system.