What is a physician?

An M.D. or D.O.: In the United States, a physician is a person with an M.D. Or a D.O. Degree from a medical school. A small number of physicians received their degrees in other countries that use abbreviations different from M.D. Or D.O., but they have equivalent degrees and so are also called physicians in america. There are other "healthcare practitioners" that are called doctors but are not physicians.

A trained doctor: Historically a physician (doctor) received training and passed examinations to attain a doctor's degree (M.D., D.O.). Recognizing the power of this attribution, many non-doctors now call themselves physician to attain a status perhaps not deserved. So you will see naturopathic physicians, chiropathic physicians, optometric physicians, etc. none of whom deserve the label. It is marketing.