Toddlers have bad dreams about being apart from their parents. Preschoolers will cry and run to their parents' bedroom. They dream about monsters or the dark. Older children will go back to sleep without waking their parents. Their dreams are often about death or real dangers.
Comfort is the best response parents can give a child that is awakened from a nightmare.
Allow the child to talk about the dream, if the child can. Stay with the child until the child is calm and falls back to sleep. If the child can talk, then ask during the day about their fears and worries. Talking can resolve stressful issues and keep them from building up in the child's mind. At bedtime for toddlers, play quietly with the child or read a pleasant story together.