The subconscious mind is a half of our consciousness that seems to have been highly accessed by ancient mankind however now is considered deeply mysterious. Reason and logic probably emerged a minimum of partly to defend ourselves against being hypnotized by ideas that were false, by enemies, etc. For the subconscious mind will not reason, it will not argue, it will not parse, it will not resist (unless it's been previously programmed either by one's own imagination or reason or an outside hypnotic force to resist a particular plan; and then, it will be re-programmed to just accept that terribly same plan).
Thus, it's among the subconscious mind that each one of our "magical" power lies. And that is why hypnosis taps the subconscious mind. Hypnosis puts individuals into one level or another of trance (though hypnotists never place folks to sleep, although the Greek root word does mean sleep), thus that they subconscious mind becomes highly accessible.
The subconscious mind is usually awake, and it's not just located within the brain. The subconscious mind is not some lower strata of the physical brain. It's the nervous system, it's the emotions, and some say that it is also "non-local", too, like an energy field that extends outward such as when folks do astral projection, or the usually spoken-of "aura". When we visit sleep, we have a tendency to enable the subconscious mind to integrate new info or ideas that are figured out or absorbed by the acutely aware, waking brain. We tend to fully would like to try to to this, and that's why lack of sleep soon comes to have horrible health consequences mentally, emotionally, and physically.
When programming is done via hypnosis--whether through a hypnotist or hypnotherapist, or through self-hypnosis (either accidentally or on purpose)--the aware mind creates images, feelings, concepts for the subconsciousness. Again, this part of the mind will not reason, use logic, or argue. It does whatever it is commanded to do--whether this is often good or bad for the person. It is up to the acutely aware mind, the logic and the intuition, to see what is good or unhealthy for oneself; and this is often terribly usually not the second nature factor that we assume it's or should be.
So, for example, if individuals have a drawback with self-image or self-confidence, this means the subconsciousness includes a "river of negativity" running through it. The subconscious facet of our minds creates our habitual behaviors, our developed skills, our consistent emotional reactions, and our habitual attitudes. Some folks even say the subconscious mind ultimately creates our each experience and our terribly environment; that it "magnetizes" into our lives whatever we have a tendency to choose to habitually, consistently imagine for ourselves with our acutely aware mind, in a "magical" way.
Hypnotism, so, uses suggestions made to someone when they are in a trance in order to plant the seeds of new (presumably healthier and a lot of productive) pictures, new experiences, inside the subconscious mind in order to form a person's life better.
