What is a kicker card in poker and how does it affect the outcome of a hand?

In Poker, a kicker card is an additional card used to break ties between players with the same hand ranking. It is the highest card that is not part of the main hand. The kicker card can affect the outcome of a hand by determining the winner when players have the same hand, such as a pair or two pairs. The player with the higher kicker card wins the hand.