It provides a quick way of tagging many files at once with coherent values if you use the checkboxes next to the items in a pane.
Make a pane for, for example, Genre. Select a bunch of files in the file list. Activate pane tagging. Click the check boxes next to the items (Pop, Blues etc.) in the Genre pane you want to assign to the selected files. Done. (The genre tag/field for each file in the selection is filled with the ticked values/items - Pop, Blues etc. - in the pane.)