Oligarchy is when multiple rulers rule the country.
Monarchy is when a king or queen is the ruler. In the olden days, an absoulte monarchy was usual. These days, the absolute monarchy has been replaced by a limited monarchy. An absolute monarchy is where the monarch can do whatever he/she wants with decisions and law-making. A limited monarchy is when a parliament is also involved in decisions regarding the country/ kingdom.
Theocracy is when the decision makers are representatives of a God or multiple Gods.
A democracy is where everyone has a say in the decisions. The population usually votes someone as a representative to make positive changes to their country.
A dictatorship is where there is one ruler who makes all the decisions. No one questions the dictator's decision as they will get punished.
Anarchy is where there is no one to rule and govern the country. War-torn countries are prone to fall into anarchy.