Rapid Eye Movement (REM) Sleep: This stage is associated with vivid dreams and rapid eye movements.
Non-Rapid Eye Movement (NREM) Sleep: This refers to all other stages of sleep besides REM, including lighter sleep (stage 1 and 2) and deep sleep (stage 3 and 4).
Hypnagogic State: This transitional state between wakefulness and sleep often includes brief hallucinations or jerks called hypnic jerks.