Hello! first time twin mom

I found out i’m having twins and was told that there’s about a 90% chance they are semi identical ? I was told they have two sacks so they’d be fraternal but possibly share the same ambilical chord so can also be partially identical ? I have 0 understanding of anything but was explained that instead of two eggs being fertilized I had one egg that split before implantation causing them to be identical but also fraternal ? anyone have some insight because i don’t understand and google is no help