Residency is a stage of graduate medical training. A resident or house officer is a physician (one who holds the degree of M.D., D.O., MBBS, MBChB, or BMed) who practices medicine usually in a hospital or clinic under the direct or indirect supervision of an attending physician. Successful completion of a residency program is a requirement to obtaining an unrestricted license to practice medicine in many jurisdictions. Residency training may be followed by fellowship or "sub-specialty" training.