Duck, there are two Houses (or "Chambers") of Congress: the Senate and the House of Representatives.

As provided for in the Constitution, each state gets two senators. Each senator now serves a six-year term.

The House of Representatives (whose members are often confusingly called "Congressmen" even though senators are equally members of Congress) is made up of elected officials who each represent a legally defined "district" within their state. Unlike the number of Senators, the number of Representatives per state is not fixed: it is based on the size of the state's population and occasionally changes.

Representatives serve a two-year term.

Senators and Representatives can run for re-election as often as their party will nominate them.

Since a Presidential election is held every four years, it will always   be accompanied by Congressional elections for senate, house, or both.

The Senate is often called "the Upper House" and the House or Representatives "the Lower House." Bills have to pass the Lower House before they are ratifed, amended, or rejected by the Upper House. Amended bills get kicked back to the House of Representives (called "the Hous," for short, to add to the confusion) for their ratification or rejection.

Once a bill is approved by both houses, it goes to the President for his signature. Then it becomes law. The President, however, can reject a Congressional bill by refusing to sign it (this is his "veto power"). That doesn't happen often, but when it does, Congress can override the veto with a two-thirds majority. Without that, the law is rejected.

Not quite as complicated as it sounds. The whole setup, plus the Supreme Court, was created in the 18th century to prevent any one person (like the President) or any coalition (like some Congressional clique) from gaining dictatorial power.