There are two different selections possible, row selection from the Row No column , and cell selection from the main spreadsheet like view of the active Edit Pane.
These two selection methods are independent of each other and we can have both at the same time.
Row Selection
Usually if we select a task that is song based and we have some rows selected in the Row No column then the task will only be performed on those rows. If no rows are selected then the task will be performed on all listed rows. Most tasks in the File, Row Edit, View and Action menu are song based.
Cell Selection
Tasks that are field based such as Copy, Paste and Set Value are always performed on the cells selected in the Edit Pane . Most tasks in the Edit menu are field based.