There are two theories in hypnosis.
One is a state theory, that is, there is an altered state of consciousoness. Altered state means a change in our mind state when we move from one consciousness to another (waking consciousness to drowsy consciousness is an altered state).
The other is a non-state theory. It is more of a psychological effect – human’s expectancy. It is like self-fulfilling prohecy – what you believe is what you get.