What is it used for?

Hypnotherapy is used for a variety of medical reasons and there are many conditions that respond well. Just as in ancient times, hypnosis still works most efficiently in cases of anxiety and stress-related disorders but it is also effective in a number of other conditions, including: asthma, insomnia, eating disorders, weight problems, gastrointestinal problems, pain control, headaches, hypertension, compulsive habits and performance/exam anxiety. Many phobias are also treatable by controlled deconditioning under hypnosis.
The more serious addictions like alcoholism and drug habituation don't respond so well because there's also a considerable biochemical problem to be overcome in these cases.