power.settings.sleep.ppkg

Windows provisioning package Reference

A .ppkg file is a Windows provisioning package. The container holds configuration settings, certificates, applications, and policies. The provisioning engine of Windows applies the package during setup or later. Administrators build packages with the Windows Configuration Designer. One package can configure many devices without a full system image.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.