Law is a set of rules enforced by society or government to regulate behavior and protect people. There are many different kinds of laws, each with its own purpose and methodology. Some are based on religion, others on social custom and tradition, some on empirical observation and analysis, and still others on intellectual intuition and creativity. In modern societies law serves many purposes, including preserving peace, maintaining the status quo, protecting minorities against majorities, promoting social justice, and providing for orderly social change. Some systems of law do these tasks better than others. For example, an authoritarian regime can keep the peace and maintain the status quo, but it may also oppress minority groups or suppress political opponents.

There are three broad areas of law: criminal law, civil law and administrative law. Criminal law deals with conduct that threatens public order and provides punishment for those who violate it. Civil law addresses disputes between individuals, such as those that arise out of automobile accidents or defamation. Administrative law relates to the activities of government agencies.

The study of law is a rich field of scholarship, with many subjects and subfields. Legal history, philosophy and theory provide insights that can inform the practice of law. The jurisprudence of particular courts, especially those that have produced many binding precedents, provides important guidance for future cases.

An important principle is the distinction between “law” and “legal authority.” Legal authority refers to the power of a court or judge to make binding decisions. A court’s decision is considered to be “law” if it is binding upon lower courts or other courts that can review the case. Exceptions to this principle, known as the doctrine of stare decisis, are rare and involve extremely complicated issues.

Among the most significant areas of law are those that deal with rights and duties of people in their interactions with one another and with property, money, and the natural world. Contract law covers agreements between people to exchange goods or services, from buying a bus ticket to trading options on the stock market. Property law defines a person’s rights and duties toward tangible things that they own, such as homes or cars.

Another broad area of law is that which deals with taxes and the financial system. Tax law includes regulations on corporate, income, and capital gains taxes, as well as rules governing the use of credit and interest. Banking and financial regulation establishes minimum standards for banks and sets best practices for investment. Regulation of industries such as utilities, energy and water is another important facet of law. It provides protections against the risk of economic crisis, such as the Great Depression of 1929. It also ensures a level of service that is enforceable. It is for this reason that there is a widespread perception that the rule of law is a fundamental necessity of any civilized society. In addition to its practical value, law is a vital subject for scholarly inquiry into the philosophy of rights, ethics, economic analysis and sociology.