Night terrors are not nightmares. Night terrors occur during the deepest phase of sleep. Many people have experience seeing spiders, snakes or scary people in the room with them. Night terrors can last from 5 to 20 minutes. Although they are asleep, their eyes may be open. They feel unable to fully awake and can be difficult to comfort. Once awake, they have no memory of the event but may have a sense of fear.
Nightmares occur during REM sleep like most dreams. Nightmares may scare the patient but after awakening, they can recall the nightmare like a long, movie-like dream.