Most people meet the securities licensing system as a list of numbers: Series 6, 7, 63, 65, 66, 24. Lists like that hide the structure underneath, and the structure is what tells you which exams you actually need, in what order, and who has to sign off before you can take them.
There are really two systems layered on top of each other. FINRA runs the qualification exams that let a person register with a broker-dealer. NASAA, the association of state and provincial securities ...