MD is a Masters/Postgraduate degree.
MS is postgraduate degree in general surgery while MD is the postgraduate degree in general medicine. Both are pursued only after MBBS.
“MS is for some fields where more of surgical expertise and skills are required. Whereas, MD is mostly non-surgical, but there are some branches where surgery can be part of MD. There are various branches where a MBBS graduate can pursue MS or MD. The decision should be taken depending on one’s choice of subject. But because of growing competition this may not be possible all the time. After MD or MS, one can join a medical college as teaching faculty, start own practice, can apply for job in government health sector or corporate hospitals”.