Do Elves Sleep?

As far as racial abilities in D&D go, one of the most interesting ones is the Elves' Trance. Because of this ability, Elves don't need to sleep like other races do. Instead of sleeping, they go into a deep, meditative state while taking a long rest.

Can an elf sleep?

Sleep is a proper subset of unconscious - elves aren't flat immune to all unconsciousness, or the rules would explode when one of them drops to 0 hit points. Elves are specifically immune to effects that specifically state they inflict sleep (or, of course, effects that only work on sleeping targets).

Do elves sleep with eyes open?

Because they aren't really asleep, their eyes aren't closed. Handy when you need to rest, but also need to stay alert of orcs and such.