Sleep terrors are episodes of screaming, intense fear and flailing while still asleep. Also known as night terrors, sleep terrors often are paired with sleepwalking. Like sleepwalking, sleep terrors are considered a parasomnia — an undesired occurrence during sleep.
Although sleep terrors are more common in children, they can also affect adults. A sleep terror episode usually lasts from seconds to a few minutes, but they may last longer.
Sleep terrors are relatively rare, affecting only a small percentage of children — often between ages 4 and 12 — and a smaller percentage of adults. However frightening, sleep terrors aren't usually a cause for concern. Most children outgrow sleep terrors by their teenage years.
Sleep terrors may require treatment if they cause problems getting enough sleep or they pose a safety risk.
Source: http://www.mayoclinic.com