Poker face is an expression used to describe the emotionless face that a person displays when playing a game of poker. A neutral expression is absolutely essential for a poker player to ensure that others cannot judge the quality of the hand that they have received, due to some signals or emotions that are visible on their faces.
Players can make a judgment and even find patterns of play, of a player, after noticing facial and bodily expressions. Therefore it is extremely important for a player to maintain a constant reaction or stay as close to a neutral expression and body language, as can be. The term poker face is also used quite frequently beyond the realm of the poker table, and in everyday life.