Let me clear things up and explain how I understand it. So there’s 3 things you might got confused with. “transmigration, transportation, reincarnation” Transmigration is basically you died in a 1st world and got into a body of someone that’s already existed in the 2nd world and continue your life with it. Transportation is I am not sure you know the anime called “Re:Zero” but it’s similar to that anime. You didn’t die in the 1st world and got teleport to the another world with your old body. Lastly Reincarnation the basic one a lot of people already know. It is you died in the 1st world and start over a new life at the 2nd world. I hope this explain it. Tbh I am not entirely sure so if I made any mistakes please forgive me.