theres different practices you can do to train your mind to stay conscious and aware while you fall asleep. And then when your body goes through all the sleep states (beta, theta, delta) you are aware of everything. Pretty much lucid dreaming. But the whole time, so your body shuts down and does everything it needs to do but your mind stays awake. Except in deep sleep (delta) your mind is no longer active. But shit some people do it to the point that they're conscious 24/7. It's called conscious dreaming, or lucid dreaming... dream yoga... ect..