An open prison is a type of penal institution where prisoners are allowed to roam around outside the walls of the prison during the day and return to their place of confinement at night. There are several synonyms for the term "open prison" such as a minimum security prison, progressive incarceration, day release prison or satellite prison. These terms describe a correctional facility that is less restrictive than conventional maximum security prisons, but still operates under strict security protocols. Open prisons are often used to rehabilitate inmates, allow them to reintegrate into society and prepare them for their eventual release.