Pinch Hitting
A bench bat hits in someone's place, and the replaced player is done.
How it actually works. The substitution is permanent, so the man coming out is out of the game, and a manager doing it in the sixth has to be able to cover the position for three more innings. That constraint, and not the hitter's ability, is what usually decides whether the move is available at all.
Why it is done, and when it is wrong. Pinch hitting is much harder than it looks and the numbers show a real penalty across the sport, because a hitter coming off a bench cold in the eighth inning is being asked to do the hardest thing in sport without any of the preparation the starters have had. Managers who compare a bench player's season line to the starter's are comparing the wrong numbers. The good uses are narrow: a platoon edge against a specializt, or a hitter whose one skill is exactly what the moment needs.
What people get wrong about it. Using the bench early empties it, and a manager who has pinch hit for two spots by the seventh has no answer left when the real moment comes in the ninth. Bench management is a resource problem across a whole game rather than a series of independent decisions.
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