In chess, pawn promotion occurs when a player moves a pawn to the opposite end of the board, reaching the eighth rank. This is a significant moment in the game, as it allows the player to transform the pawn into any other piece, typically a queen, which is the most powerful piece. The promotion process is straightforward: once the pawn reaches the last rank, the player must replace it with the chosen piece. This strategic move can greatly enhance a player's position and increase their chances of winning the game.