It’s all fine to say that every account is segregated from all other accounts. It’s nice to know your stuff is safe from the prying eyes of your coworkers or family. But what about collaboration? What if you want to give some files or folders to another account holder?
You can’t just open up someone else’s Home folder and drop it in there. Yes, every account holder has a Home folder (all in the Users folder on your hard drive). But if you try to open anybody else’s Home folder, you’ll see a tiny red 
icon superimposed on almost every folder inside, telling you “Look, but don’t touch.”
Middle: In the Public folder is the Drop Box, which serves the opposite purpose. It lets anyone else who uses this Mac hand in files to you; they, however, can’t see what’s in the box.
Bottom: Inside the Users folder (to get there from a Home folder, press 
-
) is the Shared folder, a wormhole connecting all accounts. Everybody has full access to everything inside.
Figure 13-11. Top: In other people’s Home folders, the Public folder is available for your inspection. It contains stuff that other people have “published” for the benefit of their coworkers.
Fortunately, there are a couple of wormholes between accounts (Figure 13-11):
The Shared folder. Sitting in the Users folder is one folder that doesn’t correspond to any particular person: Shared. Everybody can freely access this folder, inserting and extracting files without restriction. It’s Central Park, the farmers market, and the grocery-store bulletin board.
The Public folder. In your Home folder, there’s a folder called Public. Anything you copy into it becomes available for inspection or copying (but not changing or deleting) by any other account holder, whether she logs into your Mac or signs in from across the network.
The Drop Box. And inside your Public folder is another cool little folder: the Drop Box (not to be confused with the free online Dropbox service). It exists to let other people give files to you, discreetly and invisibly to anyone else. That is, people can drop files and folders into your Drop Box, but they can’t actually open it. This folder, too, is available both locally (in person) and from across the network.