I dont comprehend!?
Answer:
intern is the first year of your training after you receive your M.D.
then comes residency- the length vary depending on your specialty
after residency you're a staff physician. other places have different name for this, like maybe "attending physician" but the essential idea is that you're on your own. you can practice unsupervised.
sometimes relations do a fellowship after residency if they want to sub-specialize. for instance, doing a plastic surgery fellowship after finishing a general surgery residency.
If you suspend around a medical school/teaching hospital, you'll see medical students in their pre-clinical time who are necessarily just doing classwork and labs, and more advanced students (in some institutions specified as externs) who are actually within contact with patients on clinical rotations. You'll usually spot them by the short lab coats on their backs and the glazed look surrounded by their eyes.
Once graduated, doctors progress on to their residencies in their chosen specialties. The PGY-1 residents are still informally call interns, and different specialties require from 3 to 5 years of residency. Once done, most doctors move on to private practice, but a worthy number go into fellowship, usually a couple of years, in a subspecialty. Also, somebody have to teach adjectives these doctors in training, and the researcher staff are generally referred to as attending physicians. They may be contained by a strict structure with like peas in a pod heirarchy as you see on a college campus (instructor, assistant professor, etc.) and may or may not have both the intellectual post and a private practice.
This, of course, is the US model. UK have a completely different system.