There’s a common misconception that Dropbox folders are listed in a directory of drop boxes somewhere, and people can put files in and take files out anytime they want to at some mysterious location, if only someone would tell us where it is.
Dropbox is not a public post office. There is no manual of zip codes. You can’t ‘find’ people on Dropbox. Neither can you ‘view’ another person’s Dropbox files unless they want you to. You can only send files to another person’s Dropbox by having a shared folder with them. (Read about how to share a Dropbox folder.)
(As of October 4, 2012 Public folders are no longer a part of the Dropbox installation.)
You can use it or not use it. I think Dropbox intended it as a place to put all the files you want to share publicly, just as the Photos folder was/is a place to put all your photos. It’s not necessary, just a convenience.
You can do the same thing by creating a folder called XYZ. The point is in the link itself. If you publicly post a link to a file or folder in your Dropbox, it’s public.
If you share only links to individual files within the Public folder, or any folder, that’s all someone else can see. You can share the link to the whole folder in which case all the files in it, present and future, can be seen by anyone who has the link.
If you don’t have a Public folder, just create a new folder named Public. It will work exactly the same.
To share a link to an individual file within any folder:
Right-click on the file, and choose Share Dropbox link
If you installed Dropbox before October 4, 2012, it might say Copy public link instead. It doesn’t really matter. Either way you have a link to share.
The link is now on your clipboard so you can paste it into a web page or email. The person who receives this link will only be able to see the specific file you sent them a link to, not the other contents of your folder.
To share a link to an entire folder, right click on the folder and choose the same thing: Share Dropbox link.
This will copy the link to your clipboard and you can paste it wherever you want.
Think twice about whether you want the link to your entire Public folder, or any folder, made public because once you give it away you can’t take it back except by deleting the folder and its contents.
The search engines do not index these links unless they’re posted on web pages. To stop sharing a file, simple remove it from your folder.
To put a file in someone else’s Dropbox
Create a Shared Folder and invite them to it. If they accept your invitation, you can then put files into the folder on your side and they’ll show up on the other person’s computer in their Dropbox.