The repository browser allows you to navigate through the different project directories. Each project has its own root directory in the repository which cannot be deleted - unless you delete the project itself. All files and sub-directories that you want to create must be placed inside a project folder.
Directories that you create do not exist physically on the server and entire structure is stored in the database. Uploaded files however, are saved to a physical folder on your server.
By default, they are kept in:
root / media / com_joomproject / repo / project id
Navigation
At the top of the page is the nagivation where you can upload files, create new directories and notes (assuming you have permission to do so), perform bulk actions if any of the item checkboxes are selected, and filter the shown data by searching, or selecting a label. Most options will not be available until you select an active project.
Labels
The viewing access label, which shows the groups that have access to each item, is only visible to admins. Moving the mouse over the creation date or author label will show the exact creation date. Custom labels you may have selected will also be shown here.
Deleting directories
Deleting a folder will also delete its contents. If it contains an item which you are not allowed to access, this item will be moved outside of the directory you are trying to delete.