Automatic writing occurs when someone allows himself or herself to become a vessel through which messages can be channeled. 
These messages may come from the subconscious, divine guidance (such as spirit guides), or spirits. When you automatically write, you do not consciously control whatever it is you are using to create the words. Rather, you act as a scribe, allowing the information to flow through you and onto your medium.
Automatic writing or psychography is writing which the writer states to be produced from a subconscious, and/or external and/or spiritual source without conscious awareness of the content. It is a form of channeling and involves allowing Spirit, the universal mind or your higher self to simply flow through you, and to create or guide the words that you write.
Channeled writing is a very effective way to channel the spirit, as it comes directly to your hand from spirit. It is a psychic gift and one of the easiest types of psychic communication abilities to develop.