The drawing below shows that the unconscious mind (pink) takes care of the normal bodily functions, such as digestion, breathing, heart rate, and blood flow. 

The subconscious mind (blue) is where all memory from day of conception and possibly even before, is stored.  This is also where your habits and beliefs reside. 

The conscious mind (yellow) houses your rational thinking processes and also your short term memory which can hold around 6-9 bits of information at one time. 

The dotted line is the critical factor.  Think of this as the protective barrier to the subconscious mind.  It stops incoming information if that information is in opposition to the beliefs residing in the subconscious mind.  The hypnotist’s job is to bypass the critical factor to get access to the subconscious mind. 

Once in the subconscious, seemingly forgotten memory can be brought out to the conscious level.  Also, negative beliefs can be changed, suggestions for replacement of bad habits, elimination of phobias, reduction of physical pains and a host of other personal improvements can be obtained if the client is willing.