新手提问~多谢指教！

CDeviceIODlg::CDeviceIODlg(CWnd* pParent /*=NULL*/)
    : CDialog(CDeviceIODlg::IDD, pParent)              // 请问: CDialog 的冒号是什么意思，冒号后面内容有什么用？
{
    //{{AFX_DATA_INIT(CDeviceIODlg)
    //}}AFX_DATA_INIT
    // Note that LoadIcon does not require a subsequent DestroyIcon in Win32
    m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}