Dream
A dream is a succession of images, emotions, sensations, and ideas that occur during periods of REM (rapid eye movement) sleep. Although there is no consensus of thought on why people (and other animals) dream, dreams have long been a source of interest and discussion among philosophers and scientists. The formal study of dreaming is known as oneirology. Since ancient times dream interpretation has been practiced in many cultures and in the 19th century psychiatrists Jung and Freud built elaborate theories regarding the scientific study of dreams with the theory that dream images are actually symbols that represent internal conflicts.