Laws are rules which have the power of the government to back them up. The government determines what the laws are, and can assign punishments for breaking the law. Punishments can include incarceration, fines, and loss of privilege. All law determined by specific countries and governing bodies.
Crimes are actions which are deemed illegal by the government because they harm an individual or the state. These offenses are prosecuted in criminal court. The case and evidence is presented to a judge (and/or jury), who then determines the guilt or innocence of the person being tried. If the accused if found guilty the judge will determine the sentence (punishment) of the newly convicted person.
Cases that are not crimes against society are normally handled in civil court. Civil cases are normally disagreements between two or more parties. Civil law deals with contracts and lawsuits.
Labour Law addresses the legal rights of working people. Labor Unions were instrumental in the establishment of the rights of the working class. These rights include (but are not limited to) employment contracts, the minimum wage, and the safety of the workplace.
Environmental law is a complex web international bodies, groups, treaties, state, and federal laws. Environmental law deals with humans and their effects on the environment. Air, water, and land pollution are all part of environmental law.
International law is the field dealing with sovereign nations and how they deal with one another, as well as conflicts between private citizens of more than one nation. The UN is currently the most looked to international body who is supposed to establish and maintain international law.
Military Law is the law that governs various branches of the armed forces. Each country has its own way that the military handles its cases. Military law is normally handled outside of civilian courts, and the military is expected to handle its own problems. The military has its own code of conduct, laws, and court system.
Privacy law is used to determine how private information, of a private citizen, collected by a private (or governmental) entity can be used. These laws include rules for medical information, financial information, communications, and the sanctity of one's own home.
The law is ever changing, evolving, and open to interpretation. What is legal or not legal in one generation or country may be acceptable in another.