Some may be confused with the differences between MD and Ph.D. These are known to be higher degrees. Those who have these titles are considered to be more educated as compared to other people. Someone who has achieved a Ph.D. means that this person is a doctor of philosophy. This can also be used to describe the doctorate of the person in different fields.
When you say MD, this refers to a medical doctor. This is someone who has gone through med school and has already achieved all of the merits needed in order to treat patients. Take note that Ph.D. deals with researching more. Knowing this will help you to not get confused by using the two terms and titles.