Some ways a student doctor is referred to:

Interns/Students- those still in medical school. But in years 3-4
Residency(Residents)-Those through with medical school, but haven't finished their specialty yet.
Chief Resident-One in their last year of specialty and put in charge of the others.
Attending-Where the doctors watch over other residents and fellowship winners in teaching hospitals.
Fellow-Doctors that are done with their residency and are going on for more specialized learning.