Yoga Nidra means lay down in the specific position of sleeping like a Yogi. It is a state of sensible very Deep Sleep. In Meditation, you remain in the rising state of consciousness, and gently focus the mind, while allowing thought sensations, patterns, emotions, and images to arise and go on. However, in Yoga Nidra, you leave the Waking state, go past the daydreaming state, and go to Deep and deep Sleep, yet remain awake.