In American football, the purpose of a fumble during play is an unintentional loss of possession of the football by the player carrying it. When a player drops the ball without being down by contact, it creates a chaotic situation where either team can recover it. The fumble can lead to a change of possession, resulting in the opposing team gaining control of the ball, potentially affecting the game's momentum. It is a crucial aspect of the sport that can significantly impact the outcome of the game.