Poker is a card game that is often played for money. Players will make bets, usually with chips that represent a certain amount of money, and if all of the bets are "called" or matched, then whoever has the highest ranked hand wins.
There are several different forms of poker. In stud poker, usually played with 7 cards, but sometimes with 5, a player receives some cards that are hidden from other players, and some cards face up. In draw poker, all of the cards are hidden, and each player can draw cards to improve their hand. In community card games, each player is dealt "hole cards" which other players cannot see, and there are also community cards that all players share.