In academic medicine, there are many different career tracks or paths, the details of which vary somewhat by institution. Physicians in academic medicine are either on a clinical promotion track or an academic promotion track. Physicians in clinical promotion tracks can be either volunteer clinical faculty or core clinical faculty. Volunteer clinical faculty are physicians who are not primarily employed by a medical school or a university. They are usually doctors in private practice who enjoy teaching and so work with trainees, either medical students or resident physicians, in a variety of clinical settings such as their own offices, emergency rooms, or hospitals. Core clinical faculty are those physicians who are either partially or completely employed by a teaching hospital or university. Their primary responsibility is to generate revenue via direct clinical care. They may do some teaching as well. Clinical faculty do not typically have significant academic responsibilities such as writing grants and papers.