P.17 Using Dialog Boxes

A dialog box is a special kind of menu for asking you a yes-or-no question or some other special question. Many Emacs commands use a dialog box to ask a yes-or-no question, if you used the mouse to invoke the command to begin with.

You can customize the option use-dialog-box to suppress the use of dialog boxes. This also controls whether to use file selection windows (but those are not supported on all platforms).