There are 5 main types.
1) Monarchy- Rule by one, or a monarch. Determined by wealthiest person in land.
2) oligarchy- rule by a few, a group of aristocrats, or wealthy people, rule together
3) tyranny- rule by one harshly, and the person is a dictator, chosen by the people, but inexperienced with the power
4) democracy- rule by the people, where the people have the power and vote to make decisions
5) republic- aka direct democracy, and what the US uses. Elected officials make decisions based on people's problems and thoughts