Medical Resident
A medical resident is a term used for a physician in training who has completed medical school. A resident in the medical field has an M.D. or D.O. degree but does not have a full license to practice medicine unsupervised in the U.S. They are in their second, third, or fourth year of residency. Some residents can even be in medical training up to 8 years.A medical residency gives in-depth training within a specific branch of medicine, such as internal medicine, neurology, psychiatry, physical medicine and rehabilitation, and radiology.
A Junior resident or PGY-2 is a physician trainee in his or her second year of residency. Junior residents supervise and teach interns and medical students. A Senior resident is a physician trainee in his or her third year of residency or greater. Senior residents supervise and teach interns and medical students and are preparing themselves for independent practice. In some fields, such as surgery, residency can continue beyond three years to a total of eight years. There are also Chief residents in the hospital. These are residents in their final year who take on a leadership role within the residency program. Chief residents serve as an intermediary between the more senior physicians and the hospital administration.
Reference: http://en.wikipedia.org/wiki/Medical_resident