Mark's numbers are right on, but a few of the terms are "rubber words" meaning different things to different people.
NMO is national marketing organization. They have the top-level contract directly with the insurance company. They also get the production bonuses. Production requirements are steep, usually starting at $1 million +.
IMO is independent marketing organization. These are numerous FMOs (and some large MGAs) who band together to form a corporation in which they all pay to be shareholders. The
IMO itself, or a shareholder, is the NMO as well. The
IMO will take a few points off the top to cover expenses. The shareholders each get the net comp and split the bonus. Their combined production meets the quota. This is a more "traditional" definition of
IMO. Lately the term has also come to include what has traditionally been an
FMO. Shenandoah was great at doing that -- calling everyone and "
IMO", when in the traditional sense they were mostly
MGA operations.
FMO is field marketing office/officer. These organizations are typically the
IMO shareholders. They are the industry's top wholesalers. They generally work on volume with a 10-15 max point spread.
MGA is managing general agency/agent. Mark accurately points out the comp spreads and support levels, or lack thereof.
Anyway, that's my take on this pecking-order alphabet soup.
Atlantainsguy