What are the differences between each of the DoD Issuances?
A quick reference is DoD Issuances Defined: http://www.dtic.mil/whs/directives/corres/writing/DoD_Issuances.ppt . The official source for issuance definitions is DoDI 5025.01, “DoD Directives Program” located here: http://www.dtic.mil/whs/directives/corres/pdf/502501p.pdf. The Glossary section defines issuance types.