From the horses mouth:
Strengthening the nation’s capacity to detain and remove criminal and other deportable aliens is a key component of the comprehensive strategy to deter illegal immigration and protect public safety. Detention and removal of illegal aliens is a priority of U.S. Immigration and Customs Enforcement (ICE). This commitment has been backed by significant resources devoted to detention and removal efforts.
DRO secures bed space in detention facilities, and monitors these facilities for compliance with national Detention Standards. The standards specify the living conditions appropriate for detainees. These standards have been collated and published in the Detention Operations Manual (Detention Standards). This manual provides uniform policies and procedures concerning the treatment of individuals detained by ICE. Detainees in ICE custody are provided with a National Detainee Handbook, available in English or Spanish. The National Detainee Handbook provides an overview of the general rules, regulations, policies and procedures that all detainees are required to follow while in ICE custody, as well as the programs and services available at all ICE facilities. Each facility also has a site-specific handbook that is a guide to the policies, rules and procedures in effect at that specific location, and addresses day-to-day concerns of ICE detainees.
ICE.GOV
Immigration Detention Facilities