Poker is a card game played by two or more players. Each player places an initial amount of money into the pot before the cards are dealt. These are called forced bets, and they come in three forms: antes, blinds, and bring-ins. The players then each receive 2 cards face down (hidden from other players), which are their hole cards. There is a round of betting after this, starting with the player to the left of the big blind.
Each player can choose to either fold their cards and sit this hand out, call the current bet and raise it further, or bluff against an opponent. The player with the best hand wins. There are elements of gambling in poker, such as when a player is on a flush or straight draw (which require one more card to complete) and bluffing an opponent, but the game also provides a useful way to learn about uncertainty, enabling players to make better decisions in other areas of life.
I have a friend who used to be temperamental, but through poker he learned how to stay in control of his emotions and make better decisions, even when things were going wrong for him. This is a skill that he has carried into his job as a lawyer, and I think it is something that can be taught to anybody, not just to poker players. It is, for example, why I highly recommend Maria Konnikova’s book The Biggest Bluff, which is a fascinating memoir about learning to play poker in order to understand luck and uncertainty, and then becoming a champion.