The word hypnosis comes from the ancient Greek word ‘hypnos’ meaning sleep, but this is a misconception. Hypnosis is NOT sleep. It is a relaxed state with heightened awareness. Even if the person falls asleep during a session, the subconscious listens and is alert. They will return to normal consciousness when asked to, or simply awaken after a short nap. They will feel refreshed, relaxed and have no side effects at all.
In practice, people who are hypnotised often talk with the hypnotherapist and can both answer and ask questions, hear everything that is said very clearly, and are perfectly well aware. However, they may answer questions quickly and intuitively from their unconscious rather than their rational mind. This may help them get to the root causes of their issue more easily.
After the session it is likely for the person to remember what it has been said. However, like anything they hear or learn, they will retain the information that is necessary for them in the present moment. Sessions are usually recorded anyway, so a full record of the session can be provided, if necessary.