From the Document: "The National Defense Authorization Act (NDAA) provides authorization of appropriations for the Department of Defense (DOD), nuclear weapons programs of the Department of Energy, DOD elements of the Intelligence Community, and defense-related activities at other federal agencies. In addition to serving as an authorization of appropriations, the NDAA establishes defense policies and restrictions, and addresses organizational administrative matters related to the DOD. Unlike an appropriations bill, the NDAA does not provide budget authority for government activities. Nevertheless, historically it has provided a fairly reliable indicator of congressional sentiment on subsequent appropriations for particular programs. FY2021 was the 60th consecutive fiscal year for which a defense authorization was enacted. This regular enactment of complex legislation for six decades depends upon close adherence to process and consistency in procedures, schedules, and protocols."
CRS In Focus, IF10515
Congressional Research Service: https://crsreports.congress.gov/