Conscious and unconscious are terms which describe the general characteristics of a human mind. The “conscious mind” is the part of the brain where we generally “live” – the part you might think of as “you”. The little voice reading these words out loud in your head is the conscious mind. The unconscious mind is everything else!
The way hypnosis works is that it updates the unconscious mind with new, more helpful information. It is rather like reprogramming a computer. Hypnosis can change associations that the mind initially accepts. Whilst in a hypnotic trance, it could be that cigarettes, for instance, are made to no longer be seen as friends but as enemies. Hypnosis can also be used to instruct the unconscious mind to find better ways of going about things such as being better able to deal with stressful situations without having an anxiety attack for instance.
Given that the unconscious mind controls our autonomic bodily processes, it is also possible to achieve physical change through hypnosis. Pain control is a very good example. The mind has the ability to alter our awareness of pain. As an example it is well known that professional chefs who get burnt frequently, barely notice the pain unless it is a particularly severe burn. If you have ever discovered a cut or a bruise and wondered how it got there, you will have experienced your unconscious mind controlling the physical impact of the injury. Hypnosis can very effectively be used to limit pain.
Hypnosis works by allowing conversation with the unconscious mind to alter the perception of reality since the unconscious mind is where most of our problems exist but also where most of our solutions exist as well.