The term 'Ouija Board' is a trademarked name for a flat board with letters, numbers, and symbols printed on it. It is used as a tool for communicating with spirits or other supernatural entities. The term 'YES' is a three-letter word that is often used in response to questions posed to the board. It is believed that when the planchette (a small heart-shaped piece of wood) moves across the board and lands on the word 'YES, ' it is a sign that the spirit is answering the question in the affirmative.