A government ruled by a king or queen is a monarchy, although the extent to which a queen or king as power in a monarchy can vary greatly, from a "constitutional monarchy" to an "absolute monarchy".
A monarchy is a form of government with a monarch (a king, a queen or emperor) at the head, that holds supreme authority over a nation, and also performs ceremonial duties. Commonly, the position of monarch is inherited according to a statutory or customary order of succession, usually within one royal family, and the monarch rule until death or abdication, however, there are some cases in which monarchs are elected or appointed but not for the people but for a group of eligible people, like it happened when electing the Holy Roman Emperors.
