A hand is the body part at the end of an arm. Most humans have two hands, usually with 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. Many other animals have hands that can hold things, especially other primates. Human hands can do things other hands cannot.
The word "hand" is also used in cardgames. A "hand of cards" is a group of cards that one player can see but others cannot. A "hand", meaning the width of a hand, is also an old unit of measurement.