Hypnosis goes back to the ancient Greeks and derives from the Greek word for sleep - Hypnos. The sleep is not the same as your night time sleep, but, as I was taught, a state of deep, profound relaxation.
It is important to understand that you are in control and not your therapist. Some people think that a Hypnotic trance means they will be unconscious or fast asleep. Nothing is further from the truth. You will be awake, alert and conscious at all times. Probably more alert than when you are not in Hypnosis.
Your therapist cannot make you do anything that is against your moral or ethical beliefs.