Poker is a game of cards, similar to how chess is a game of pieces. That seems to be accurate, but in no way captures the core of the game. In poker, cards are just one of the player’s tools.
Hence, the most popular kind of poker is now No Limit Texas Hold’em (NLTH or NLTH). “No Limit” refers to the fact that you may go all-in (“all-in” in poker vernacular) in any position (with the exception of literally 1-2) during your turn.
Typically, nine individuals sit at a table during a tournament. And since one of the most important aspects in poker is where a player sits (“position”), it is customary to choose the “batton” before to the start of a tournament or game day.