Hi Nadia, Monochrionic, means one egg ( so Identicle twins), or in the terms of presentation one chrion ( like an egg shell, the thick "outer sack" of the uterus) and Biamniotic( or diamniotic)means two amnionic sacks ( like a double yoker egg, the thin "inner sack" of the uterus)
Means the babies are identicle,but have their own sacks, but separated by only a very fine "onion thin" membrane

My DH describes it as the same house, separate bedrooms, unlike fraternal twins, that have their own houses!!!