Corns and calluses are caused by repeated excessive pressure or friction on a certain point of the foot. This may be due to ill-fitting footwear, foot deformities or certain walking styles that predispose the foot to increased pressure or friction.
For example, if you have a low-arched or flat foot, this may put more pressure on the inner part of the foot when you walk, which may lead to the development of foot corn or callus on the inner side of the heel.
Having foor corn does not necessarily result in pain, most people tend to have some form of callus on their feet. However in some individuals, this can lead to some discomfort or pain.