Monarchy- a form of control in which the people are headed by one ruler, usually a king, who takes power legally and often hands the throne down to his son. Oligarchy- a form of government in which the people are managed by a small group of people, often affluent aristocrats. This isn't usually very helpful to the preponderance of the population.
Tyranny- a form of state very comparable to a monarchy, but a tyrant doesn't take power authorized and can challenge no right to the throne. A tyrant usually doesn't pass power to his son, and notwithstanding common stereotypes, not all despots were bad leaders.
Democracy- a form of government led by the people, either through representatives or directly. Democracy in ancient Athens was a direct democracy, in the USA now we have a democratic democracy.
aristocracy: the highest class in particular societies, typically involving people of noble birth holding ancestral titles and offices.