In general, a bill goes through the following stages before it becomes a law (we are assuming that it completes all of the stages and does in fact become law).
- The bill is introduced. This is done by a member of Congress who submits the bill to his or her respective house of Congress.
- Referral. The bill is referred to a committee. The committee can refer it to a subcommittee.
- Markup. The committee discusses the bill and can change it if they see fit.
- Reporting. The committee reports the bill to the whole house. It typically gives a recommendation about how to vote.
- The bill is debated and voted on by the full house.
- Reconciliation. If the two houses have passed bills that are not exactly identical, members of the houses must meet and iron out the differences.
- President signs the bill (or refuses to sign it and lets it become law unsigned).
This is the basic story of how a bill becomes a law. A much more detailed account can be found here.