What it is: fr/Wikipedia

A lucid dream is a dream in which one is aware that one is dreaming. The term was coined by the Dutch psychiatrist and writer Frederik (Willem) van Eeden(1860–1932).^[1] In a lucid dream, the dreamer can actively participate in and manipulate imaginary experiences in the dream environment.^[2] Lucid dreams can seem real and vivid.^[3]

A lucid dream can begin in one of two ways. A dream-initiated lucid dream(DILD) starts as a normal dream, and the dreamer eventually concludes it is a dream, while a wake-initiated lucid dream (WILD) occurs when the dreamer goes from a normal waking state directly into a dream state, with no apparent lapse in consciousness.

Lucid dreaming has been researched scientifically, and its existence is well established.^[4][5]

for more fr/Wikipedia, go to:    http://en.wikipedia.org/wiki/Lucid_dream

Also, here is an interesting site for lots of information and research on Lucid Dreaming:   http://www.lucidity.com/