From the Background: "The Future Years Defense Program (FYDP) is a projection of the forces, resources, and programs to support Department of Defense (DOD) operations. The FYDP is compiled every year and typically completed during the 'programming' phase of the Planning, Programming, Budgeting, and Execution (PPBE) process. The program is updated during the 'budgeting' phase to reflect DOD's final funding decisions presented in the annual President's budget request. The FYDP captures resource management decisions for projected DOD activities associated with normal, peacetime operations. Grouping funding by programs--rather than activities, as depicted in the annual budget justification documents--the FYDP reflects the planned allocation of DOD resources to major strategic efforts over a multiyear period."
CRS In Focus, IF10831
Congressional Research Service: https://crsreports.congress.gov/