Final answer:
Night terrors are sleep disorders involving horrible hallucinations and feelings of panic, occurring in stage 4 NREM sleep, and are classified as parasomnias.
Step-by-step explanation:
The disorder that involves horrible hallucinations and typically occurs during stage 4 sleep, which is a phase of non-rapid eye movement (NREM) sleep, is known as night terrors. Night terrors are classified as a type of parasomnia, which is a group of sleep disorders involving unwanted, disruptive motor activity and experiences during sleep.
Those experiencing night terrors suffer from a sense of panic and may scream or attempt to escape from the immediate environment, often without memory of the event afterward. Night terrors are different from nightmares, which occur during REM sleep, and are more intense and frightening.
The disorder described in the question is night terrors. Night terrors are a parasomnia sleep disorder that occurs during the NREM phase of sleep. During night terrors, the sleeper experiences a sense of panic and may scream or attempt to escape from the immediate environment.