The emergency medicine physician is what we may recognize from television as the emergency room (ER) doctor. This physician diagnoses and treats acute illnesses or injuries that require immediate medical attention. This sometimes involves resuscitating patients and ensuring they're stabilized, then pairing them with the appropriate specialist who can treat their condition long term.
While emergency medicine may be a specialty, the ER doctor needs to be a generalist, since a wide variety of conditions, from accident and assault-inflicted injuries to undiagnosed illnesses and diseases, will present at the emergency room.
Emergency medicine physicians usually have credentials as primary care physicians, and they can be trained in other specialties, as well.