/effect: Gives entities a status effect like Speed for a number of seconds, or clears their effects.
Syntax
<angle brackets> are required, [square brackets] optional. /effect has 3 forms:
/effect <player: selection> <Mode: cleareffects> [effect: effect]
/effect <player: selection> <effect: effect> [seconds: int] [amplifier: int] [hideParticles: boolean]
/effect <player: selection> <effect: effect> <Mode: addinfiniteeffect> [amplifier: int] [hideParticles: boolean]