Hypnosis is a natural state of mind you experience every day, just before you go to sleep, as soon as you wake up, when you are watching TV, when you are daydreaming, when you are immersed in reading a good book, or when your mind is so focused on some inner experience that the external environment begins to fade away.
This altered state of consciousness makes it possible for the hypnotherapist to work on changing behaviours or emotions which have become problematic. For example, if you have to prepare for a presentation and feel overwhelmingly nervous about it, you can learn how to access and strengthen your ability to relax and apply that to the situation of making a presentation. Once you know how to do that, then it becomes easier to “decide” how you would like to feel and react in a given situation.