Fapfolder, a folder on your desktop computer or camera filled with pictures used mainly to masturbate on.
May include nudes and semi-nudes, but can also include pictures of people of interest fully dressed or even pictures of things unrelated to anything sexual.
Usually named something random or that won't draw any attention like 'Submap 12' or 'fhiwufhiwefh' to make it less awkward when people see your desktop.
Eric: 'Hey Joey, what is this map 'Submap 12' on your desktop?'
Joey: 'Euh, nothing'
Eric: 'Its your fapfolder, isn't it!'