Rapid eye movement (REM) occurs when you are asleep and when you are dreaming your eyes move to see the images in your dream which your brain is thinking of. Usually 25% of sleeping is dreaming and...
Rapid eye movement (REM) sleep-- A phase of sleep during which the person's eyes move rapidly beneath the lids. It accounts for 20-25% of sleep time. Dreaming occurs during REM sleep.
Non-rapid eye movement (NREM) sleep-- A type of sleep that differs from rapid eye movement (REM) sleep. The four stages of NREM sleep account for 75-80% of total sleeping time.