What are the Texas Holdem kicker rules and how do they impact the outcome of a hand?

In Texas Hold'em, the kicker is the highest card that doesn't contribute to a player's hand. If two players have the same hand, the kicker is used to determine the winner. For example, if two players both have a pair of Aces, the player with the higher kicker card wins. Kickers can impact the outcome of a hand by breaking ties between players with the same hand ranking.