In poker, a kicker is a high card that is not part of a hand’s main combination but still counts among the best five cards. Its job is to break ties between hands of the same rank.
Take a Texas Hold’em example. The board shows K♠ 9♦ 6♣ 3♥ 2♠. Player A holds K♥ Q♣ and Player B holds K♦ J♦. Both have a pair of kings, so the kickers decide: A’s queen beats B’s jack, and A wins the pot. Kickers can come from the community cards as well as from a player’s own cards. If both players’ best five cards are exactly the same, for instance when the board’s high cards play for both, the pot is split.
Kicker strength is why ace-king is worth more than king-jack before the flop. Poker software works out kickers automatically, which removes arguments over split pots at online tables.