What is the difference between a nightmare vs night terror?

Stages of Sleep. Nightmares are scary or disturbing dreams that occur during what is known as rem sleep, which is the part of sleep during which most dreams occur. People are ofthen able to recall the events of nightmares. Night terrors are events of vague distress that occur during the deep stages of sleep. People usually have little or no recollection of these events, other than feelings of distress.