People who have experienced a night terror know that the experience is completely different than the more common nightmare. A night terror involves sudden awakening from sleep, screaming, sweating, confusion, rapid heart rate, inability to explain what happened, and usually no recall of "bad dreams" or nightmares. A person who has a night terror may have a vague sense of frightening images. Many people see spiders, snakes, animals or people in the room, are unable to fully awake, difficult to comfort, with no memory of the event on awakening the next day.
Nightmares, on the other hand, occur during the dream phase of sleep known as REM sleep. Most people enter the REM stage of sleep sometime after 90 minutes. The circumstances of the nightmare will frighten the sleeper, who usually will wake up with a vivid memory of a long, movie-like dream. Night terrors, on the other hand, occur during a phase of deep non-REM sleep usually within an hour after going to bed. During a night terror, which may last anywhere from five to twenty minutes, the person is still asleep, although the sleeper's eyes may be open.