The United States government is known as a republic or representative democracy. The U.S. Constitution is a written document that outlines how our government works. It was written after we declared independence from England and won the Revolutionary War. It can also be changed or amended and this has been done 17 times after the first draft was approved.
Our government is split into three parts (often called branches)
Executive branch - President, Vice President, and his cabinet. They are in charge of enforcing the laws of our country.
Legislative branch - This branch is referred to as Congress. It is made up of 100 Senators (2 from each state) and 435 House of Representatives (elected from states according to population). They are in charge of making the laws.
Judicial branch - 9 Supreme Court justices appoint for life and the lower courts in each state.