Front Left -- Poker is a family of card games that share betting rules and usually (but not always) hand rankings. Poker games differ in how the cards are dealt, how hands may be formed, whether the high or low hand wins the pot in a showdown (in some games, the pot is split between the high and low hands), limits on bets and how many rounds of betting are allowed.
Many poker players feel that this betting system distinguishes poker from gambling games. With the minor exception of initial forced bets, money is only placed into the pot voluntarily by a player who, at least in theory, rationally believes the bet has positive expected value. Thus while the outcome of any particular hand is determined mostly by chance, the long-run expectations of the players are determined mostly by their actions chosen based on probability and psychology.