Essentially, the sweat evaporates off their bodies and condenses on the ceiling. This then rains down in this foggy-cloud type thing. Essentially, everybody's combined sweat and various fluids that come out on the dance floor is in the air and has covered EVERYBODY!
This feels like this filmy goo on your skin. Hence the name, "raver goo" (and it makes your leg warmers and pants all dirty)
Pretty much everybody is grossed out, but is still there because they love the music and want to dance.
In this space, people try to avoid that really high guy who dances with his shirt off. (they are really gross to bump into cause they are slimy) or anyone who has painted themselves with body paint, (cause it wrecks your costume/outfit)
"Yeah, it's pretty gross in there. Hey hurry up, I'm starting to get cold inside. We can warm up in there"