> ...tried to help someone with a computer issue they were having with their Windows computer- I had NO IDEA where their "Pictures" folder was, or why I kept seeing the same file in multiple places as I clicked around the file explorer. I also feel like I was confused about something to do with "Desktop", but I don't quite recall what it was. It was honestly pretty disorienting- I thought I was in a weird carnival house of mirrors.
As I understand it, there are actually N+1 of all these categories of "semi-magical" directories on-disk -- where N is the number of different users registered on the machine -- but each user only sees (and has to care about) two of each category. And the confusing bit is that Windows tries to make it look, to each user, as if there is only one of each.
That is: There is a "Pictures" directory for each user, stored in something like C:\Users\<<TheirUserID>>\Pictures. Then there is also a shared C:\Users\All Users\Pictures directory (though see further below at [1]!) for, well, pictures that you want all users to be able to see... And finally, to top it off, there's the "virtual Pictures directory", kind of an alias (or Shortcut, in Windows lingo) to two directories at once: the users own, and the shared one. Just to make it look all un-confusing and user friendly, "here's the Pictures folder, where you keep your pictures". Road, paved, etc...
So, N+1 Pictures directories where each user interacts with their own + the shared one -- and likewise for the other "magical" per-user-plus-a-shared-one directories: Desktop, Start Menu, Music, etc.
> I don't honestly know --right now-- if you can save a file to one of these virtual "Pictures" places or not.
Oh yes, sure you can.
> Or, if you do, where it would actually go.
AFAIK, the default is the user's own directory; if they want to make it shared for all users on their machine, they have to jump through the hoop of explicitly digging out the "All Users\Pictures" directory to save to.
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[1] Now, that said, this is apparently based on out-of-date information: As I looked through my Windows 10 box to check on the directory names right now, I noticed that "C:\Users\All Users\" is apparently also, in turn a "shortcut" (=alias) nowadays, pointing to somewhere in C:\ProgramData... So the above is as of now an oversimplification. But AFAICR that was actually how it worked, with the shared all-users directory being an actual physical directory on disk, in Windows NT, 2000, and I think XP. Dunno when it changed; maybe with Vista, 7, or 8.