A hand is the part of the body at the end of an arm. Most humans have two hands. Each hand usually has four fingers and a thumb. On the inside of the hand is the palm. When the fingers are all bent tightly, the hand forms a fist. The joints that are the hardest part of the fist are called knuckles.Have you ever cracked your knuckles?You should try it.;-) Human hands can do things other hands cannot.