Law is a system of rules that are created and enforced through social or governmental institutions to regulate behavior. The precise definition of law is a matter of long-standing debate.
The purposes of law vary widely across nations and are often based on the history, culture and beliefs of a people. These purposes include keeping the peace, maintaining the status quo, preserving individual rights, protecting minorities against majorities, promoting social justice and providing for orderly social change.
Legal systems vary widely, with a civil law tradition covering over 60% of the world and religious laws used in a small number of countries. The most common sources of authority in modern civil law systems are legislation, particularly codifications of constitutions or statutes passed by governments, and custom.
Congress is the lawmaking branch of government and makes laws through a process that involves research, discussion, changes, and voting. A bill becomes a law after it is introduced in one chamber and passed by the other.
A law that is passed by Congress is designated as a statute and receives a number in the order it is signed by the president. The lawmaking process for federal laws is different than state or local laws.
Laws serve many purposes, but in order for a law to be effective it must be valid and apply to all people, not just the ones who make it. A lapse of time can cause a law to be obsolete, or it may be derogated (or overturned) by an authoritative body.