A Ouija board is a parlor game of slumber party fame. It facilitates automatic writing, which many believe is a means of channeling answers to questions from the spiritual realm.
Does using a Ouija release powerful demons from some sort of otherworldly lock hold? Allow humans to access a spiritual realm? Or just exemplify the "ideomotor response," a psychological phenomenon through which our subconscious brain drives our fingers? Many questions...so few answers... Sticking to the linguistic realm, we can tell you that what's happening when you use a Ouija is called "automatic writing," and that marketers of the original boards claimed the term Ouija itself derived from an ancient Egyptian word for "good luck," though any casual observer can see that the word was formed from combining the words for "yes" in French and German ("oui" + "ja"), tying into the "yes" and "no" that appear on the board itself. A note on pronunciation: Either "wee-gee" or "wee-ja" is acceptable.