Monarchy is the oldest form of government in the United Kingdom. In a monarchy, a king or queen is Head of State. The British Monarchy is known as a constitutional monarchy. This means that, while The Sovereign is Head of State, the ability to make and pass legislation resides with an elected Parliament.
A monarchy is a kind of government where a monarch, a kind of hereditary ruler (someone who inherits their office), is the head of state. Monarchs usually rule until they die or pass down (when a monarch resigns it is called abdication). Most monarchies are hereditary, but some are elected.