Learn here about the control and history of the Roman government.
Roman Republic
When the roman republic was first set up, the people in charge were 2 men named consuls. (A consul is an official appointed by the government of one country to look after another its commercial interests and welfare of its citizens in another country.) Woman are not allowed to be consuls. The consuls controlled the army. They decided to start a war and decide how much money the taxes would be. They both would have to agree in order to change anything. If one of the consuls said "Veto" Latin for "I forbid it" nothing would be done.
Julius Ceaser
By about 50 B.C. the time of Julius Ceaser, generals had begun to take over the government and ignore the consuls or Senate, and do just as they pleased. They could do that because they had an army to help them.
Augustus 31 B.C.
In 31 B.C. Augustus was one of the generals during the time when the other generals began to take over. But he realized the people didn't like to be pushed around, and so he set up a new system (but still where he had a all the power). Augustus kept the Senate and consuls, but he made the Senate vote to make him in charge. That way he could Veto anything the Senate tried to do. Thus making a new Government
Emporers
Although Senate's and consuls had most of the power and Augustus could veto (forbid) anything the Senate tried, the Emperor had the real power.