Mono-Di - identical ?

KT • Pregnant for the first time with identical twins ❤️❤️
So at my last Dr appointment after we found out it was twins , he told me they were mono-di but would be fraternal... He didn't see the ultrasound pic, just got the report from the ultrasound tech . My impression was that mono di were identical :), they are in different sacs, but are sharing a placenta ... Thoughts ?