Somnambulism is the technical term for sleepwalking.
The term itself is derived from Latin root words "somnus" (meaning "sleep") and "ambul" (meaning "walk"), making the compound Latin and English terms nearly perfect parallels to one another (Dictionary.com).
Sleepwalking occurs in children and in adults and usually happens during non-REM sleep, according to the U.S. National Library of Medicine. The frequency of sleepwalking decreases for children as they grow into adulthood (ibid) and further decreases with age in adults (Psychology Today). In most cases, somnambulism is not considered to be a serious or threatening condition.
Somnambulism is technically considered to be a "sleep disorder."
What causes somnambulism?
Fatigue, lack of sleep, and anxiety are all associated with sleepwalking.
Although medical science is not entirely certain of all the causes of sleepwalking, these are the prominent factors.
Somnambulism has been treated as a device in fiction where it is often used to create a situation of intrigue where a character is uncertain if he or she has carried out an action in his or her sleep. This device is used in the aptly titled, "Somnambulism" by Charles Brockden Brown. The ironic situation wherein a character is not aware of his or her own actions generates suspense and thus is used in stories and films that emphasize suspense and anticipation (the genres of mystery, horror, and thriller).
Basically this is sleepwalking. Sleepwalkers normally walk around in the night and have no idea what they are doing. Some terrible cases of sleeping walking include people walking out of the front door at night without a clue and waking up elsewhere. This is not considered dangerous, but is still a large deal in the community today.