From isaac sim to real robot or vice versa

After having played around with isaac sim on omniverse I don’t understand the bridge between the simulation and the real robot. I have ROS code that works on the real franka emika panda for example, but how does this interface with Isaac sim, does it have an ip I can use instead of the real robots ip. And if I were to go the other way and develop code with the python api, how would this code then be used on the real robot?

Kind regards,
Thomas