Hi Ashfak ,
MBBS is an undergraduate course of 5 .5 years. The degree achieved is of MBBS .
After completing MBBS , one has to appear for competitive exams for post graduation. Medicine , Surgery , ENT (otolaryngology) are few of the many branches whiche one can pursue his/her career in. In easy words , in order to become a surgeon it is must that his/her MBBS is completely done.

Hope your cofusion is clear.