A "Yellow Card" is a warning issued by referees in sports, particularly in soccer and rugby. It indicates that a player has committed a foul or unsportsmanlike behavior. Receiving a yellow card serves as a caution, and if a player receives two yellow cards in a single match, they are shown a red card and must leave the game. Yellow cards are part of the disciplinary system in sports to maintain fair play and respect among players. They help referees manage the game and ensure that players adhere to the rules. Accumulating multiple yellow cards over a series of matches can lead to suspensions.