Under its Constitution, the United States of America is a federal, representative, democratic republic at the local, state, and national levels. It is Federal because power is shared by the local, state, and national governments. It is Representative because delegates are elected by the people by free and secret ballot, and it is Democratic because the people govern themselves Republic because the U.S. government derives its power from the will of the people.

Article I of the U.S. Constitution states that Congress will consist of two separate houses. A lawmaking body with two houses is called a bicameral legislature. The two houses that make up the U.S. Congress are the House of Representatives and the Senate.

Congress is the primary lawmaking body in the U.S. government. To solve problems, Members of Congress introduce legislative proposals called bills or resolutions. After considering these proposals, Members vote to adopt or to reject them. Members of Congress also review the work of executive agencies to determine if they are following government policy, and may introduce new legislation based on what they discover.

Bills accepted by both houses of Congress and by the President become law. When the President vetoes a bill and returns it to Congress, Congress reviews the reasons for the rejection but may still act to pass the bill. The U.S. Constitution allows Congress to override the President's veto with a two-thirds majority vote of both the House and the Senate.