Law is a set of rules enforced by a government and used to ensure a peaceful society. It serves four main purposes: establishing standards, maintaining order, resolving disputes and protecting liberties and rights. Laws can be enacted by government or private individuals and can be enforced through fines, imprisonment or other sanctions. It is a complex subject, and its precise definition is the subject of many books and debates.

Different kinds of law are practised throughout the world, influenced by local culture and history. Some countries, such as the United States and England, have a common law system that relies on decisions made by judges in cases that come before them. These are compiled and become case law, which is not open to individual interpretation. Other countries, such as Japan, have a civil law system that uses written codes that judges must follow when making decisions.

Legal systems also vary in the way power is distributed between the executive, legislature and judiciary. Some governments, such as the United States, have a constitutional framework that defines the balance of power among these three branches of government. Others have no such document and instead rely on the law as it develops from statute, case law and convention to determine how much power each branch of government has.

Various kinds of laws are practised in the fields of business and money, including intellectual property law, land law, family law, company law, trusts and commercial law. Other important areas of law are criminal law, immigration law and asylum law. These laws affect the rights and privileges of people to live, work, travel or reside in a nation-state that is not their own and to gain or lose citizenship.

There are also different types of law that regulate specific activities such as banking, insurance and the utilities. Banking and financial regulation sets minimum standards for banks to follow and rules on how best to invest money in companies and businesses. Other regulated industries include energy, gas and water. Governments can also use the law to control the activities of private companies that perform public services, such as electricity, water or telecoms. In the field of social policy, laws can be used to restrict the freedoms of citizens and control dissent. For example, censorship and crime and punishment are two examples of such controls. The law can also serve to protect people from other people, such as by preventing terrorism and other crimes.