CoreKernel is the indivisible minimum kernel (controlling the processor, memory and critical hardware)

    Kernel includes everything else that runs in the kernel (e.g. logical kernel abstractions including threads, processes, etc., networking stack, device drivers, printer drivers, graphics & media drivers, KTM, ETW, etc.)

    CoreOS is the core (mostly user-mode) OS substrate upon which the OS itself depends (e.g. Win32, COM, OLE, RPC, WMI, DirectX, etc.)

    OS is the remaining set of other high-level essential and non-essential features that may, or may not, be installed by the OEM/user/etc. (e.g. Explorer, Silverlight, .NET, Media Center, IIS, etc.)