Kicker
Also known as: Kickers
The side card that breaks ties between otherwise equal hands. With matching pairs or trips, the higher kicker wins — this is what makes **AK beat AQ** on an ace-high board.
What a kicker does
When two players hold the same rank of pair, trips or quads, the hand is decided by the highest unmatched side card — the kicker. Both players make the best five cards; if their made portion ties, the next card down resolves it.
Top pair, top kicker (TPTK)
Hitting top pair with A♠K♠ on a K♥ board gives you top pair, top kicker — the strongest non-set one-pair hand, because no worse kicker beats yours.
Kicker trouble & domination
The flip side is domination: A♠Q♦ is crushed by A♠K♦ when an ace flops — same pair, your kicker loses. This is why offsuit aces with weak kickers play poorly out of position and why kicker strength matters more than the overpair / set / trips tiers above one pair, where the kicker is often irrelevant.
Example
Board A♣9♦4♠. You hold A♠K♠, villain holds A♥Q♣. Both have a pair of aces — but your king kicker beats his queen, so you win the pot. Swap your hand to A♠5♦ and you are now the dominated one.