veto

      One part of "how a bill becomes a law" is the presidential veto. To start at the beginning, a bill becomes a law when it is passed by both houses of congress ( the Senate and the House of Representatives ) and signed by the President. If a bill passes both houses of congress and the President doesn't agree with it, he may return the bill to the Senate or House of Representatives, and explain his objections to it. This is called a veto. It is described in the United States Constitution, Article I, Section 7, although the word "veto" isn't used.
    If the President "vetoes" a bill, the House and the Senate may alter the bill, and pass an amended version on to the President for his signature. Or, the House and Senate may override a presidential veto by passing the same measure, but by a 2/3 majority, instead of a simple majority. A 2/3 majority would mean 2 out of every 3 persons voting voted to pass the bill--for example, 20 for, 10 against, or 200 for, 100 against. . A simple majority means the side with 1 more vote wins--51 to 50, for example.
     Another way a bill might become a law is if the President ignores it when it is presented to him for his signature. If the President doesn't sign or return the bill within 10 days, it becomes law as if he had signed it, provided that Congress is still in session.
     If you're interested in reading more about this, see your local newspaper's section on "area votes in Congress", or check out the Congressional Record.