This is were one person has complete control and is the leader of their contry. This one leader can do whater they want over that country. A pro about this is that the leader can make up their own rule instead of having to agree with another leader. If they would have to agree with another leader than it might cause a fight or something.
This is where a group of people come and rule a county together. A con is if people don't agree on the same the same thing when trying to make a rule. A pro is that not one person has to struggle to make a rule. This is the most effective to me because people are together making rules and ideas together.
Rule by many is when a king or queen rule that country but don't have full power. A pro is that they can countol the counrty together, however the con is that they don't have full power.