Monarchy
The most common form of government from ancient times to the early part of the 1900s was monarchy, or rule by a hereditary king or queen. The root word "mono" means one so a monarchy is a government ruled by one royal person such as a king, queen, emperor or empress. To protect their power from the church, who wanted to be able to make laws too, kings proclaimed that God had given them the right to rule. This means that kings and queens were born with "The Divine Right of Kings" and because of their royal blood they were made the only rulers by God.
In a monarchy, change in leadership happens when power is passed down to the first born child (usually a male). This is called inherited (hereditary) power. If someone who is suppose to inherit the power doesn't want it they can abdicate, meaning give up, the throne to the next person in line.
In some traditional monarchies, the monarch has absolute or complete power over people. But a constitutional monarchy, like the United Kingdom (Great Britain), also has a democratic government that limits the monarch's control and people have more rights and responsibilities.
Present-day monarchs are nearly all symbolic rather than actual rulers of their countries. In such monarchies as Great Britain, governing power is now in the hands of the national parliaments (legislature). If Queen Elizabeth were to die or abdicate (give up) the throne the power would go to her oldest son Prince Charles.