From the Document: "The Department of Defense (DOD) offers certain 'quality-of-life' benefits to military members, their families, and retirees. The general purpose of these benefits is to attract, retain, and support morale and readiness for military service members. One of these benefits is worldwide access to grocery and retail stores--called 'commissaries' and 'exchanges'--typically located on military installations. Commissaries provide subsidized groceries and household goods to eligible patrons. Exchanges sell goods for profit, similar to a department or specialty store, but use some of this profit to fund various Morale, Welfare, and Recreation (MWR) activities."
CRS In Focus, IF11089
Congressional Research Service: https://crsreports.congress.gov/