The three main components of the U.S. criminal justice system are law enforcement, courts, and corrections. Law enforcement includes federal, state, and local levels which are responsible for investigating crimes and making arrests. Courts are divided into two parts - federal and state court systems, each with tiers of courts having different responsibilities. Corrections includes four main types - probation, jail, prison, and parole - each responsible for supervising offenders. The overall main purpose of the U.S. criminal justice system is to enforce laws, adjudicate criminals, and punish and rehabilitate offenders.