Corrections institutions are organized in tiers by level of government and, at each level (federal, state, and local), specific types of institutions provide corrections functions based on the relative severity of the offenses committed. The most restrictive form of corrections is incarceration in a prison. Both the federal and the state governments operate their own prison systems; within the federal government, the military maintains its own prisons. Prison inmates serve time for serious offenses and are incarcerated for a year or longer.

In contrast, most people sentenced to jail serve less than a year for misdemeanors and offenses against the public order. Jails are operated at the local level—by cities and counties. The federal government operates some jails as well, and within the federal government, the Bureau of Immigration and Customs Enforcement has its own detention facilities. In some states, jails and prisons are operated under a single state authority, but the distinction—prisons for long terms and for serious offenses, jails for lesser terms and for less serious offenses—is still maintained.

Probation is the most common form of corrections without incarceration and is one form of what is known as "community corrections." In addition to holding offenders for short terms of confinement, jails also serve other purposes, including:

• Receiving individuals pending arraignment and holding them awaiting trial, conviction, or sentencing
• Readmitting probation, parole, and bail-bond violators and absconders
• Temporarily detaining juveniles pending transfer to juvenile authorities
• Holding mentally ill persons pending their movement to appropriate health facilities
• Holding individuals for the military, for protective custody, for contempt, and for the courts as witnesses
• Releasing convicted inmates to the community upon completion of sentence
• Transfering inmates to federal, state, or other authorities
• Housing inmates for federal, state, or other authorities because of crowding of their facilities
• Operating community-based programs as alternatives to incarceration
• Holding inmates sentenced to short terms (generally under one year)