Lucid dreaming is knowing that you are dreaming while you are sleep-dreaming.
It is the idea of becoming 'awake' in your dreams.
Stephen LaBerge is an expert on the topic from the point of view of the academic world.
His salient work Lucid Dreaming is a guide on how to develop skills so that you can lucid dream. He provides a series of simple techniques to utilize that can aid in helping you recognize that you are dreaming with the same sense of recollection that you have while awake.
In 1988, acting on his conviction that lucid dreaming offers many benefits to humanity, Dr. LaBerge founded the Lucidity Institute, the mission of which is to advance research on the nature and potentials of consciousness and to apply the results of this research to the enhancement of human health and well-being.
From the Tibetan Buddhist point of view lucid dreaming is well known. It has been part of Tibetan Buddhism for centuries.
It is used as a means for doing various spiritual practices while the practitioner is asleep. Its not easy but they do it.