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, and other defense-related activities. 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. (As of the date of this publication, Congress has not passed an FY2022 NDAA.) This regular enactment of legislation for six decades depends upon adherence to process and consistency in procedures, schedules, and protocols."
CRS In Focus, IF10515
Congressional Research Service: https://crsreports.congress.gov/