There are three main types of law, with sub-categories within each, such as Civil Law, Criminial Law, and Administrative Law.
According to the Encarta World English Dictionary, the definition of the word law (noun) is:
Binding or Enforceable Rule: a rule of conduct or procedure recognized by a community as binding or enforceable by authority
Piece of Legislation: an act passed by a legislature or similar body
Legal System: the body or system of rules recognized by a community that are enforceable by established process
Synonyms: rule, regulation, decree, act, edict, ruling, commandment, directive, bylaw