Before a law can be passed, a member of Congress must introduce a bill, a joint resolution, or a concurrent resolution. The most common form of proposed legislation is a bill. A bill originating in the House is referred to by the abbreviation “H.R.” for House of Representatives and then followed by a number. For example, H.R. 100 is the hundredth bill introduced in that particular session of the House of Representatives. A bill originating in the Senate is abbreviated “S.” followed by a number.

Any member of Congress (the House or Senate) can introduce a bill when the body is in session. The bill must then pass both Houses of Congress in identical form. This can be a difficult process, as members of each House may have strong positions about particular language in a bill.

Once a bill has been passed with identical language in both Houses, it goes to the president for signing. If the president signs the bill, it becomes law. If the president refuses to sign the bill into law, he exercises his veto power. If the president vetoes the bill, then Congress can override the presidential veto by passing the measure with a two-thirds majority.