The United States has a bicameral legislature or Congress composed of the Senate (100 seats; 6-year term, with one third of membership renewed every 2 years) and the House of Representatives (435 seats, 2-year term).
Bills may be introduced by a member of either chamber. Typically, the first stage in the approval of a bill involves consideration by a committee. If approved (reported) by the committee, the bill reaches the floor of the chamber. Once a bill is approved by one chamber, it is sent to the other, which may pass, reject or amend it. In order for a proposed bill to become law, both chambers must agree on identical versions of the bill, and the President must sign it. If the President vetoes a bill, the veto can be overturned if a two-thirds majority of both chambers votes to do so.