Hypnosis is simply a state of relaxed focus. It is a natural state. In fact, each of us enters such a state - sometimes called a trance state - at least twice a day: once when we are falling asleep, and once when we are waking up. That kind of fuzzy, timeless state between dreaming and awake is a trance state. When a nine-minute snooze-button seems to give you enough time to have an-hour long dream, that's a trance state.
There are many other times that people enter a natural state of trance. Driving, watching TV, listening to music, working on a favorite hobby or activity in the "flow" state. These are all "altered states of consciousness," and all are various levels of trance. Trance is normal, natural and common.
Some people leave their first hypnosis event saying, "I wasn't hypnotized - I knew what was going on the whole time!" Well of course you did! Hypnosis is not a state of amnesia or of no awareness. Just the opposite true, in fact: hypnosis is a state of very heightened awareness and focus.
Hollywood has perpetrated many myths about hypnosis, and not remembering anything from the hypnosis session is one of those myths. Only under special circumstances would a person forget everything from a session.
Much more can be accomplished when the person undergoing hypnosis remembers everything.