Hypnosis is a state of mind in which our unconscious mind is able to more freely communicate with our conscious mind. It is naturally occurring in everyone and is a state of mind in which a person is relaxed, focused and receptive. Any time someone becomes totally absorbed in something like watching a film, reading a good book or simply day dreaming, they have slipped into a natural state of hypnosis. It is typified by an altered state of awareness in which a sense of time is lost and the unconscious mind becomes more accessible or dominant. Brain waves alter and move into the lower frequencies of alpha and theta depending on how deep the level of hypnosis becomes (delta is a sleep state). There are many levels of hypnosis and often only a light hypnotic state is required to gain access to our unconscious mind.
In Hypnotherapy, a client is guided into hypnosis by a Hypnotherapist purely to unlock and release potential therapeutic benefits available through accessing their own unconscious mind. A trained hypnotherapist will always do this in a professional manner ensuring the client remains aware, in total control and has complete memory recall.
Trance is another term that has become synonymous with hypnosis and many Hypnotherapists use this expression in place of hypnosis.