Wholly Within selects items that are entirely contained inside the rectangular boundary of a fence selection.
Wholly And Partially Within selects the items that are entirely contained inside the rectangular boundary of a fence selection, and items that cross the boundary.
Holding the Ctrl key down while performing a fence selection adds the selected items to the existing Graphical Selection.
Holding the Shift key down while performing a fence selection removes the selected items from the existing Graphical Selection.