Please note that this is the Narutopedia's article on the technique used by Orochimaru. If you are looking for the article on the technique used by the Kedōin Clan then you should head to Face Copying Technique.
This technique was developed for spying with grisly effects. The user applies their hand onto the subject's face, stealing its features and making it their own. Since what is stolen is the face itself, the disguise is achieved through facial feature alteration and won't reveal even the tiniest flaw. The victims of this technique are reduced to faceless corpses. The user can even change their voice to sound like that of the victims, making a very convincing copy. However, with enough force, the face can wrinkle and tear to the point of the user's actual face being shown underneath. The face can be peeled off at any point.
This technique, which leaves its victims faceless corpses, is reminiscent of the Noppera-bō from Japanese folklore. Also known as a zunbera-bō, this ghost resembles a human with no face.