The kind of human or animal ghost that is an actual sentient being is called an apparition. Many of these beings are restless because they do not know that they have passed on due to unexpected events that ended their lives, or believe they have unfinished business to attend to. Many occupy places they lived during life. Some do know that they are dead, and may come back for reasons of revenge, or to comfort or warn a loved one of some kind of impending disaster, or to lead them to some fortune or treasure.