Hypnosis is a state of focused concentration during which a person becomes less aware of their surroundings. Hypnotherapy is the use of hypnosis to treat physical or psychological conditions.
During a hypnotic state (trance), a person may be more likely to accept suggestions that can help change their behavior. A therapist can lead the hypnosis. Or a therapist can teach you to hypnotize yourself (self-hypnosis). You can also learn self-hypnosis by following instructions from online resources or books.
Experts do not know how hypnosis works. It seems to put the body in a state of deep relaxation. Hypnosis does not work for everyone.