Let’s try to understand that OS X is designed as a multi-user operating system, but still keeping your private documents, it is not easy for user A to access User B’s documents. To make it simple, let’s make an example, if Bill and Chris share a Mac, Bill will not be able to see the contents of Chris’ Documents folder while working in his account. If Bill tries, He’ll see that Chris’ Documents folder will show a red “no trespassing” icon indicating that his way is forbidden.
There are several ways for Bill to access Chris’ documents. Maybe Bill could do this for example, change permissions on another account’s folders if he knows that account’s administrator password. Or log in as root, which give you permission to access everything on the drive. But All of these techniques are sneaky enough and only some sorts of people could do these techniques.
Mac OS of course considering the condition when one user want to share their documents with another user on their Mac. So public folder is created to handle this condition. Unlike the other folder that have a red symbol on it, this public folder has no red icon. This is the place to save some documents that you want to share with other users. When someone in another account wants to do something to the documents that you’ve placed in the Public folder, they only have to open it and copy its contents to their account.
You can also save files to other users by dragging files to the Drop Box folder in each user’s Public folder. This is a “one-way” folder in that you can copy files to another account’s Drop Box, but only the person logged into that account can see the folder’s contents.
There are a couple of ways to do if you want to make files available to anyone using the computer. First, drag files to another drive or partition attached to the Mac. Second, use the Shared folder inside the Mac’s Users folder (found at the root level of the startup drive).
The Shared folder was designed for you to move files between accounts easily. You can created an alias of the Shared folder and placed it in the Finder sidebar, make it easier for you to move files between accounts