It may be surprising to many to learn that we experience trance states often during the course of our lives. Even passing into ordinary sleep involves a kind of trance state. The experience of hypnosis is similar: neither asleep nor awake and a little like daydreaming, with a pleasant feeling of deep relaxation behind it all. Hypnosis is a different state of consciousness which you can naturally enter so that, for therapeutic purposes (hypnotherapy), beneficial corrections may be given directly to your unconscious mind.
In this way, hypnosis is an effective way of making contact with our inner (unconscious) self, which is both a reservoir of unrecognised potential and knowledge as well as being the unwitting source of many of our problems.
Realistically no-one can be hypnotised against their will and even when hypnotised, a person can still reject any suggestion. Thus hypnotherapy is a state of purposeful co-operation.