Rather than hypnosis being a state like sleep, it is for most people a wakeful state and one in which attention is focussed and awareness heightened to a state of suggestibility.  Studies show that brain activity changes at this time with beta waves decreasing and the heart rate slowing, showing more sleep patterns than conscious ones and yet allowing for lucidity. The conscious mind takes a back seat and the subconscious mind opens up.  The achievement of a relaxed state where the mind is open and the client willing to take on suggestions is what is needed for the desired effect.