Hypnosis, also referred to as hypnotherapy or hypnotic suggestion, is a trance-like state in which you have heightened focus and concentration. Hypnosis is usually done with the help of a therapist using verbal repetition and mental images. When you're under hypnosis, you usually feel calm and relaxed, and are more open to suggestions.
Hypnosis can be used to help you gain control over undesired behaviors or to help you cope better with anxiety or pain. It's important to know that although you're more open to suggestion during hypnosis, you don't lose control over your behavior.