Simply stated, automatic writing is a free-flowing message sent by an entity in the form of the written word via a person. It is sometimes called 'trance' writing, because it is done quickly and without judgment. The person may appear in a trance-like state, putting down whatever comes to mind. This is accomplished with a writing implement and paper or a computer and keyboard. The messages may be in a language foreign to the person's own native tongue and the handwriting can be unrecognizable to the person penning the words. It may also be lacking spaces and punctuation. Pictures or symbols may be part of the writing as well.
Automatic writing allows the person access to the entity for guidance. It can also serve to retrieve information from your unconscious and/or provide insight.