A physician is a simply doctor is a professional who practises medicine
You must have to be smart to be a doctor. How long do you have to go to school to become one?
I'm not sure but their field is concerned with promoting, maintaining, or restoring health through the study, diagnosis, and treatment of disease,
Can you specialize in a certain field of medicine?
Yes, Physicians may focus their practice on certain disease categories
Do they make a lot of money?
of course, they can also be general practicioner and be  responsibility for the provision of continuing and comprehensive medical care to individuals, families, and communities
Do they need a license to practice medicine?
Yes,  the role of the physician and the meaning of the word itself vary around the world