There are three basic types of law in the United States:
Constitutional law is the law in the U.S. Constitution and state constitutions. It includes such fundamental rights as freedom of speech, freedom of religion, freedom of expression etc. The U.S. Constitution is the supreme law of the United States. No law can be enacted that contravenes the provisions of the U.S. Constitution.
Statutory law is law enacted by legislature. Congress, state and municipalities all have legislative bodies that make laws. It is created through a formal lawmaking process and codified in official text. ( Example: When the Florida Legislature passes a bill, such as the recent primary seat belt law - it is a Staturtory Law.)
Common law, began in England when law was derived from common practices. Common law includes "judge-made laws" and relies on judicial precidents (case law). Judges, thus, in their decisions are bound by precedent: the rulings of other judges in similar cases decided earlier. (All the states except for Louisiana are common law states, Florida is a common law state).
For more information on a similiar topic:
What is the difference between criminal and civil wrongs?