When you invoke this command from the DRAW menu, it prompts you to click on a field, and then draws a deep shadow (7 pixels thick, lower and right edges) for that field.
This looks best with Rectangle fields, i.e. fields whose style is "rectangle" and which therefore already have a thin visible border. Deep shadowed fields look good in organization charts, for example.
When you use the command button instead of the menu, no prompt will be given.