Okay, kiddo, a gay bathhouse is a place where grownups who are attracted to other grownups of the same gender go to meet each other and have some fun.
It's like a big building with rooms and showers where people can hang out together and maybe do things like hugging or kissing or even things like cuddling or having sex.
But it's important to remember that all of these things only happen with the consent of both parties involved. Nobody should ever touch you or make you do anything you don't want to do, and it's the same for grownups too.
These places can be a safe and welcoming environment for people who might not feel comfortable being themselves in other places. But, always remember that it's important to be safe and respect others' boundaries.