A more thorough explanation:

The Defense Commissary Agency, abbreviated as DeCA, is a part of the United States Department of Defense. Its main responsibility is to provide goods and services to members of the armed forces at lower prices than what is available in the civilian market.

For example, a member of the military can purchase groceries, household items, and other goods at a commissary store on a military base. These items are often sold at a lower cost than what is available at a regular grocery store.

The Defense Commissary Agency helps military families save money on everyday items, which can be especially important for those who are on a tight budget. By providing access to affordable goods and services, DeCA helps support the well-being of military personnel and their families.