AOA certification means that the AOA has given their blessings.
In order to practice medicine you need a license. Each state has their own licensing board. All states have the requirement that 1.) you have an MD or DO degree and 2.) you've completed a PGY-1, or intern year.
In order to become board certified, you need to 1.) complete a residency in some specializing board and 2.) pass the specialty board exam. DOs can take either the MD or DO specialty boards.
In order to get AOA certified, you need to have completed your PGY-1 year in a traditional, rotating DO internship. Being AOA certified doesn't mean jack in terms of being able to practice medicine. The only exception to this is that there are 5 states where DOs have to have done their PGY-1 in a DO internship.
Its not a dumb question. There are many mysteries in the field of medicine. Part of becoming a doc is learning to speak the language, which includes this sort of stuff. Some of it can be more confusing than biochem.
