These both are postgraduate degrees, can be done only after successfully completing mbbs degree course.
MD is doctor of medicine ,it includes both clinical and non clinical branches.. clinical branches are such as  General medicine, radiology, paediatrics,TB and chest, dermatology etc
While non clinical branches includes biochemistry,pathology, physiology, psm, etc .

MS stands for master of surgery, it also includes both clinical and non clinical branch.. clinical branches are such as General surgery, Obs. and gynae, ENT, opthal, etc
While non clinical branches includes Anatomy, etc.

Hope you understood.

Good luck..