Other forms: criminal laws
Criminal law is the legal branch that deals with crimes. If you stole an ice cream truck, drove it across state lines, and then ate all the ice cream, you'd be subject to criminal law.
The legal system has two parts: civil law, which covers private rights and disputes, and criminal law, which encompasses criminal activity. Break a law, and your punishment will be decided using the standards of criminal law. There are different rules and procedures in the two branches, from hearings and trials to sentencing.