Well, I can't simplify more than the title.
This spell sends creatures into a magical slumber. Roll 5d8; the total is how many hit points of creatures this spell can affect. Creatures within 20 feet of a point you choose within range are affected in ascending order of their current hit points (ignoring unconscious creatures).
Starting with the creature that has the lowest current hit points, each creature affected by this spell falls unconscious until the spell ends, the sleeper takes damage, or someone uses an action to shake or slap the sleeper awake. Subtract each creature's hit points from the total before moving on to the creature with the next lowest hit points. A creature's hit points must be equal to or less than the remaining total for that creature to be affected.
And the Bugbear Chief (from the Monster Manual) has a feature that states:
Heart of Hruggek. The bugbear has advantage on saving throws against being charmed, frightened, paralyzed, poisoned, stunned, or put to sleep.
The thing is: the only sleep inducing effect I am aware of is the sleep spell, which does not require any saving throw. So, this last part of the Bugbear Chief seems useless, since the only effect inducing sleep won't be affected by his advantage at all.
Sure, it could be there preemptively for future content or even in case someone homebrews such effects, but, other than that, are there any other (official/published) sleep-inducing effects other than the sleep spell? In particular, any that does require a saving throw? These could be poisons, monster or class features, magic items, or other spells that I'm not aware of.