The heel is the back part of your foot, below your ankle. It's the rounded, cushioned area that hits the ground first when you walk. Your heel bone, called the calcaneus, is actually the largest bone in your foot. It absorbs tremendous force: when you run, your heel can strike the ground with three times your body weight.

The heel of a shoe is the raised part at the back that your foot's heel rests on. High heels lift the back of the foot higher than the toes, while flat shoes like sneakers have low heels. Cowboys wore boots with raised heels to keep their feet secure in stirrups while riding horses.

In everyday speech, if someone says “close on your heels” or “hot on your heels,” they mean following right behind you, the way a faster runner might be catching up. When something brings someone to heel, it means making them obey or follow orders, like training a dog to walk beside you with its head near your heel. If someone digs in their heels, they're stubbornly refusing to change their mind or give in, planting themselves firmly like pressing their heels into the ground.

The word can also mean a selfish or untrustworthy person, though this usage is less common today.