I think it's intended to be interpreted this way:
"Straight" = "Of interest to straight men" (This includes both Male/Female and Female/Female material)
"Gay" = "Of interest to gay men" (This consists of Male/Male material)
Why is it like this? Because there are no girls on the internet. Duh.
Okay, all joking aside, OBVIOUSLY, there's bound to be at least one girl-- maybe more-- who happens to get on this site from time to time, but for the most part, it's fairly safe to say that this site is predominantly used by guys. THIS HAS BEEN A PUBLIC
SERVICE HURRVICE ANNOUNCEMENT. WE NOW RETURN YOU TO YOUR REGULARLY SCHEDULED PROGRAM.