A bill is written in the Senate or House of Representatives and sent to a committee. The House or Senate of Representatives and Capitol Hill on it's version. The House and Senate presents the final version of the bill. The bill is sent to The President to be made into a law. The President vetoes (refuses to sign) it and sent it back to congress. Congress can decide to veto if each house passes the bill again by a small vote.

How a bill becomes a law