According to The Dictionary of Occupational Titles, a hypnotherapist is a professional that facilitates change in an individual through the clinical use of the brain-wave state referred to as hypnosis.
Despite its sometimes-dubious reputation by those influenced by television and movies, hypnosis is a very natural state. When compared to other methods, it is the most effective technique to address weight loss, habit control, past trauma removal, and limiting behaviors.
Why do people need a hypnotherapist? In short, when your will is in conflict with your imagination, your imagination will win.