I think folder is the official Windows term, and most people are non-technical people who use Windows, so if you have to pick a term, it seems the more accessib

I think folder is the official Windows term, and most people are non-technical people who use Windows, so if you have to pick a term, it seems the more accessible one. If you think that is bad, I think on my smartphone there is no file browser by default, so the closest thing you have is media specific stuff, like albums, lol. So you can't even use the term folder if you are on the phone or emailing with a smartphone user of your apps...