Out-of-the body experiences are often taken for dreams and vice versa.
In reality both conditions are entirely different altered state of consciousness. Dreams are characterised by synchronic movements of the eyes (Rapid Eye Movement (REM)), the augmentation of the cerebral activity and cardiac frequency, hormonal secretion and diverse patterns of brain waves.
The most recent theories of dreams analyse it as a biological necessity allowing the brain to reorganize it-self while sleeping and permitting the release of daily tensions as much as the re-organisation our memories.
Dreamers are Passive Observers
Contrary to Out-of-Body Experiences dreamers are generally passive observer of their subjective perception with no control over of the events of the dreams. This is an entirely different condition from lucid Out-of-Body Experiences or Lucid Dreams most of the times. Common dreams are a state of the brain while OBEs are a condition experience out-of-the body generating a great sense of freedom and well being among other phenomena.
If someone is dreaming of having an out of body experience it is only a dream not a real OBE experience. The mental activity of Out-of-Body Experiences are utterly different from the subjective condition of dreams and are closer to the condition of the Lucid Dreams. In Lucid Dreams some level of awareness and control can be achieved but the consciousness is generally unable to achieved a better degree of uninterrupted lucidity contrary to OBEs experiences that can induce a remarkably high level of awareness and control entirely different from dreams, dreams of OBEs and lucid dreams.
Putting these distinctions aside, it is important to note, however, that dreaming of having an Out-of-Body Experience can sometimes be an OBE that was experienced with a lower level of lucidity out-of-the body and it is for this reason perceived as dream. They are times where you can notice, throughout the development of a dream, the separation from the human body making your dream disappear to give way to a lucid projection out-of-the body.
The IAC provide extensive information during the Consciousness Development Program (CDP) to allow students to practically differentiate such altered state of consciousness.