instCardWindow is a pre-defined PinballY object representing the Instruction Card window in the user interface. This is a window that can be optionally opened to show the apron instruction card for the currently selected game at any given time. (This is a separate top-level window, not the separate pop-up graphic overlay that the user can bring up within the playfield or backglass window via the "Instructions" command. That's not a separate top-level window, just a graphic overlay on those other windows.)
This object provides the common window methods and properties. It doesn't currently have any additional properties or methods beyond the common set.