When using Kiosk with systems that have multiple displays available, these options allow you to specify which display should be used:
Show on Main Display - This is the default option, and will show Kiosk on your main display (the one with the menubar and dock).
Mirror on All Displays - When selected, Kiosk will automatically enable display mirroring while the browser window is visible, causing all displays to show the same content. This can be very useful if you have enabled Presentation Mode.
Show on Specific Display - This option will allow you to specify which display to use, which may be helpful when using a MacBook with an external display as a kiosk.
If you wish to prevent the screensaver from activating if the computer is left idle, you may enable this option. Kiosk will automatically disable the screensaver while the browser is open, and re-enable it upon closing the browser.