After 200 years, hypnosis is still somewhat of a mystery. No one fully understands how and why it works.
Have you ever been so absorbed in an activity that hours have gone by without you being aware of it? When you finally looked at the clock you were shocked by the amount of time that had passed. During this activity, you were fully conscious, but somehow your intense focus blocked out all the extraneous stimuli around you. You were so in alignment with what you were doing that the siren of an ambulance right outside your house didn't deter you from your focus.
This feeling is similar to the feeling you'll experience when you're hypnotized by a trained hypnotist or if you learn to hypnotize yourself. You go into a trance-like state of consciousness. You're deeply relaxed and due to that relaxation your conscious mind tends to take a back seat. You're able to focus intently on the suggestions the hypnotist provides you. You're able to block out distractions and exclude the constant mental static of numerous conflicting thoughts. In this state, your subconscious mind, the part of your mind that uses pictures and imagination instead of rational thought, is easier to access.
Deep hypnosis is very similar to the relaxed state you feel right before you drift off to sleep. You're still awake and aware at the fuzzy edge between consciousness and sleep but your spirit almost seems to float above your body.
When you're hypnotized, your body is so calm and centered that the hypnotist can give you suggestions that you can mentally and physically manifest. You can feel these suggestions as if they were real. For example, if the hypnotist suggests that there's an ice cube melting on your arm, you'll feel it. In a sense, all hypnosis is self-induced. The hypnotist is simply guiding your mind into the hypnotic state, but it's your mind that takes itself into that state. You can't be hypnotized into doing something you feel is immoral. You're still aware of everything that's happening.
With practice, you can learn to put yourself into the deep level of relaxation that will yield a hypnotic state. While you're under self-hypnosis, you can provide yourself with positive suggestions that will help you to solve problems or to manifest changes in your life. These suggestions can come from your own repeated affirmations or through the help of an audio with subliminal messages.