The sub projects addon allows you to create unlimited “nested” projects.  This means that you can create sub folder within sub folders.  So if you were to look at “Dashboard > Folders”, you may have a directory with a structure that looks similar to this:


This nesting of folders allows for better organization of files.  You can also add sub folders under “Documents > User Files”.

“Projects” and “directories” and “folders” are all the same.