http://en.wikipedia.org/wiki/Lucid_dream
A lucid dream, also known as a conscious dream, is a dream in which the person is aware that he or she is dreaming while the dream is in progress. When the dreamer is lucid, he or she can actively participate in the dream environment without any of the inhibitions or limitations that otherwise would feel natural to persons who incorrectly believe they are in the "real" waking world. Lucid dreams can be extremely real and vivid depending on a person's level of self-awareness during the lucid dream.
