Doctor is an academic title that originates from the Latin word of the same spelling and meaning. The word is originally an agentive noun of the Latin verb docere ‘to teach’.
It has been used as an academic title in Europe since the 13th century, when the first Doctorates were awarded at the University of Bologna and the University of Paris.
Having become established in European universities, this usage spread around the world. Contracted “Dr” or “Dr.”, it is used as a designation for a person who has obtained a Doctorate (e.g. PhD). In many parts of the world it is also used by medical practitioners, regardless of whether or not they hold a doctoral-level degree.
A physician (American English), medical practitioner (Commonwealth English), medical doctor, or simply doctor, is a professional who practises medicine, which is concerned with promoting, maintaining, or restoring health through the study, diagnosis, prognosis and treatment of disease, injury, and other physical and mental impairments.
Physicians may focus their practice on certain disease categories, types of patients, and methods of treatment—known as specialities—or they may assume responsibility for the provision of continuing and comprehensive medical care to individuals, families, and communities—known as general practice.
Medical practice properly requires both a detailed knowledge of the academic disciplines, such as anatomy and physiology, underlying diseases and their treatment—the science of medicine—and also a decent competence in its applied practice—the art or craft of medicine.
In modern medicine, a surgeon is a physician who performs surgery. There are also surgeons in podiatry, dentistry, orthodontics, and the veterinary medicine.
Source : Wiki