Fwf stands for "friends who fuck", a more specific term for friends with benefits. Friends with benefits can mean different things, so you would use fwf to be more specific to hooking up. Fwf is used the same way as fwb (friends with benefits) , usually when texting.
Stands for "friends who fuck", used when you want to be more specific than fwb (friends with benefits). You're not dating, you're just friends who occasionally hook up. Usually used when texting someone about your relationship status.
Hey, are you guysdating or what?
Nah, we're just fwf.
Oh, okay.