Automatic writing is a phenomena whereby a person who undergoes hypnosis is given some instruction by the hypnotist to write out something that the person himself may not even know or aware of (eg certain literature).
During the hypnosis, the subject is being told that his hand is independent and has nothing to do with his mind. He is then instructed to write out a given topic. The person will then scribble down on a notebook.
Upon emerging from hypnosis, the person has no conscious memory of what had happened and is also very surprised that he is capable of writing out the given topic and find it hard to believe that it all come from him.