A demon (or daemon, daimon, Greek: δαίμονας, i.e. evil spirit), also known as an angel of darkness or a dark angel, is a supernatural malevolent being in many world religions. The word 'demon' has different meanings all over the world, but often there is the idea that they are spirits that lived in a place, or went with a person. The word is also used for a type of computer program that does useful things in the background of a computer, but this use is not related to the religious meaning.