From Academic Kids
The heel is the prominence at the posterior end of the foot. It is based on the projection of one bone, the calcaneum, behind the articulation of the bones of the lower leg. In the long-footed mammals, both the hoofed species (unguligrade) and the clawed forms which walk on the toes (digitigrade), the heel is well above the ground at the apex of the angular joint known as the hock. In plantigrade species it rests on the ground.
A heel is the projection at the back of a shoe which rests below the heel bone. The shoe heel is used to improve the balance of the shoe or for decorative purposes. Sometimes raised, the high heel is common to a form of shoe often worn by women but sometimes by men too. The high heel is sometimes supposed to originally have been invented for riding boots to prevent the boot from slipping out of the stirrup. See also stiletto heel.
The end-pieces of bread in a loaf are sometimes referred to as the heel.