This is a PPWIZARD command line switch.
This switch can be used to turn off output to the console (a "quiet mode"). If an error is detected the console is switched back on!.
If you turn the console off then I would recommend that you also use the /ConsoleFile switch to capture console output (works whether or not console output disabled).
If you just wish to reduce the amount of output and not remove it altogether then have a look at:
Note that output reduced with the above methods will not appear in any console file created with /ConsoleFile.
If the "YesOrNo" parameter is not specified then it defaults to "Y", otherwise one of the following values is expected: