In broad, general terms, the mind may be said to have two parts, the conscious and the subconscious.

Hypnotherapy works by bypassing the conscious mind and accessing the subconscious mind.  The subconscious mind is very powerful, and is susceptible to suggestion. 

This means that people with, for example, phobias or fears, who experience constant pain or who lack self-confidence or self-esteem can, through suggestions given to the subconscious mind, modify their behaviours and attitudes and even learn to control pain.  

Many people seek out hypnotherapy for help with smoking and body weight issues.

Clinical Hypnotherapy is quite different from the sort of hypnotism you see on television.  During the treatment you will experience a state of relaxation but will be aware of where you are and what is happening.