Lexicon

A minion is a creature that is under the direct command of another creature. Rather than use hit points, minions have a Damage Threshold (DT) equal to 5 + their Constitution modifier + their level (minimum 1). If they take this much damage or more after immunities, resistances, and resistance rolls are taken into account, they are stunned for 1 round. If they take this much damage while already stunned or if they take twice this amount of damage or more, they are killed or knocked unconscious depending on whether the blow was intended to be lethal or not. A minion that's been knocked unconscious remains as such until some effect or rest that would normally return a creature with 0 hit points up to 1 affects them.

Minions are typically considered to be 4 levels lower than they actually are for the purposes of calculating their challenge rating.