Bathroom fan exhaust vent

Installing new fans and there isn’t existing venting in attic to the outside. I’m going to install a vent on the roof and connect insulated pipe to the fans.
Two questions. Can I connect both fan vents together and into the same vent in the roof. Secondly I’ve heard you are supposed to create a “loop” in the insulated pipe. Where do I create the loop? What’s the purpose of it? I’ve heard it’s so condensation doesn’t make its way back or something. Sorry I couldn’t be more specific. A