A Non-Commissioned Officer, commonly refered to as an NCO, is a member of the Star Command command structure who has completed Basic Training but not attended Star Command Academy or completed compulsary courses whilst doing on-the-job learning.
Whilst an NCO can be placed anywhere in the command structure, usually they will always be placed in a junior position to an officer who has graduated from the Academy.
NCO Ranks
A Chief Warrant Officer is always made a member of the Joint Chiefs of Staff alongside other Flag Officers. This officer is always referred to as the "Senior NCO."