The form of government ruled by a king or queen is called a monarchy. In a monarchy, the head of state is usually a hereditary figure, possessing varying degrees of power depending on whether the monarchy is absolute or constitutional. Absolute monarchies grant full control to the monarch, while constitutional monarchies limit their powers, delegating authority to a constitution or elected parliament. Monarchies have deep historical roots and exist in various forms around the world, and they often symbolize national unity and identity. Modern monarchies may also focus on ceremonial roles rather than governing authority.