whats the difference between a MD degree & a MBBS degree?

Answer 1

Generally, they're essentially the same, while one is a doctorate and the other is a bachelors.

Different educational systems. Both are needed to practice as a doctor.

US only has the MD.

In countries with a MBBS (like the UK), you may be able to get an MD, but that's more for research and it comes after the MBBS.