A theory of explanation might treat explanations in either a realist or an epistemic (that is, anti-realist) sense. A realist interpretation of explanation holds that the entities or processes an explanation posits actually exist--the explanation is a literal description of external reality.
Officers in pay grades O-1, O-2, and O-3 with more than four years of prior cumulative service in an enlisted or warrant officer grade are paid increased wages using the special pay grades of O-1E, O-2E, and O-3E, respectively.
Federal employee pay varies significantly depending on your education and experience on the job. A well-established general schedule pay scale, or GS, outlines the wages of federal employees by placing them into 15 distinct pay grades, which includes all job titles.