Our brain is divided into two hemispheres, the left and the right. The left governs the concrete side of our behaviour: logic, reason, writing, maths, rationality and analysis. The right hemisphere manages the abstract side of our behaviour: dreams, intuition, imagination, creativity and emotions. Both hemispheres are in constant communciation with each other.
Despite the exchanges between the sides of our brains, it's difficult for us to control the commands our brains give us. In effect, the right side remembers everything, while the left side forgets certain things, often leading to confusion in the analysis of our behaviour.
For example, take the case of the girl who absolutely hated vegetables. She remembered being ill when she was 5 after she ate ratatouille. Her therapist found out that it was the same day her grandmother had died. Her left brain had mixed up the death and bad digestion. Once this has been established, the hypnotherapist sent the correct message to the right brain through hypnosis.