The folder Structure is predefined by your administrator. It is very similar to familiar tools like the Windows Explorer or the Mac Finder.
Permissions are set on a top-level basis and are the same in all subfolders.
There are also structural folders which cannot contain any files but are convenient for structuring content.
And last but not least there are „Inboxes“ - everyone hast write access to these Folders.
You can add a whole folder to a lightbox by right click on the folder icon.