Can Explain What This Is?

[BeastlyHex]

I Know It Opens A GUI Window Saying Goodbye, Cruel World. But Can Somone Explain What Each Part Means And Does For E.g. WINAPI and WinMain(HINSTANCE,

  #include <windows.h>

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 
    LPSTR lpCmdLine, int nCmdShow)
{
    MessageBox(NULL, "Goodbye, cruel world!", "Note", MB_OK);
    return 0;
}

Thanks

[Zexd]

http://msdn.microsoft.com/en-us/library/windows/desktop/ms633559(v=vs.85).aspx

Google is a very nice thing you can use :P