From Xojo Documentation
Displays the Screen by "pushing" it over the parent Screen passed.
Show displays a new Screen over the current Screen, placing it on the "stack" so that the back functionality of the new Screen can be used to go back to the previous Screen. If you need to just change the current Screen without affecting the stack, you can do so by using the MobileApplication.CurrentLayout property.
Use the Close method to close the new Screen and go back to the previous Screen.
Displays a new Screen: