The actions section of the Rename dialog is where you can enable other rename actions besides the primary pattern-based operation (which is controlled by the mode section of the dialog).

The options that you enable here will affect your rename operation no matter which of the primary modes you've chosen. The transformations are applied after your pattern-based operation (you can think of the rename procedure as happening from top-to-bottom down the Rename dialog).

More:
Numbering Files
Rename Macros