A pawn majority is a situation where one side has more pawns than the opponent on one side of the board, making it possible to create a passed pawn through straightforward advances and exchanges.
For example, if White has two pawns on the queenside against Black’s one, White can push those pawns, force exchanges, and produce a passed pawn — a pawn with no opposing pawn in front of it on its file. That passed pawn becomes a permanent long-term threat that ties down the opponent’s pieces to defensive duties.
In practice, a pawn majority becomes decisive in the endgame, once pieces have been traded off and pawns take centre stage. Identify which flank your majority is on, activate your king toward it, and advance your pawns methodically to convert the structural advantage into a concrete passed pawn.