Hi,

During medical school students spend about 2 years doing clinical rotations on various hospital services to graduate. These are called clinical clerk ships

After medical school these physicians work under supervision in hospitals and clinics taking care of patients, somewhat like an apprenticeship in which they gain clinical experience and knowledge to qualify for specialty board certification and independent licensure.

This is called residency training, the first year of which is called an internship . A person can apply for a medical license after the internship year (Prior to that they have a training license) The length of residency training varies by specialty. Often advanced specialty training is called a fellowship. so, a person does 3 years of residency in internal medicine and then a 2–3-year fellowship in another sub-specialty to become a cardiologist for example. Hope this helps.