Night terrors differ from nightmares in that the sleeper partially wakes terrified and confused from a night terror and fully wakes from a nightmare with the ability to describe the dream content. The two are similar in that they both cause feelings of fear and terror.
Stressors such as anxiety, medication and illness usually cause nightmares, which are vivid events that wake the sleeper from REM sleep. A person with a night terror is difficult to waken from a deep sleep and usually does not respond to voices or remember the events in the morning. A night terror lasts roughly 15 minutes, then the sleeper usually falls back asleep.