What does Kicker mean in poker?

The kicker is the highest unpaired side card used to break a tie when two players hold the same primary hand rank. Poker hands are always five cards, so when the ranked portion of two hands is identical, the remaining cards are compared in descending order to decide the winner. Worked example: you hold A-K and an opponent holds A-Q. The board comes A-9-5-2-7 with no flush or straight possible. Both players have a pair of aces, so the hand is settled by the next card. Your king outranks the opponent's queen, so your hand reads A-A-K versus their A-A-Q, and your king kicker wins the pot. Had the opponent held A-K as well, the result would be a split pot, because the five-card hands would be identical. Why it matters: kicker strength is one of the most underappreciated factors in starting-hand selection. So-called kicker problems arise when a player enters a pot with a weak holding such as A-4 and pairs the ace, only to be dominated by an opponent with a stronger ace and a better kicker. The danger is that the weaker hand often makes top pair, feels strong, and pays off the better kicker, losing a large pot. The lesson is to be cautious with top pair and a poor kicker, particularly out of position and against tight opponents who would not contest the pot without a quality holding. See also domination, top pair and starting hands.