About DDX_Control() and CONTROL in rc file

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C++

Visual-Studio

VS2010

Part of the code is as below:

IDD_CONNECTOBJECT_DIALOG DIALOGEX 0, 0, 280, 142
STYLE DS_MODALFRAME | WS_POPUP | WS_VISIBLE | WS_CAPTION | WS_SYSMENU
EXSTYLE WS_EX_APPWINDOW
CAPTION "ConnectObject"
FONT 8, "MS Sans Serif"
BEGIN
    CONTROL         "",IDC_OPCDATACTRL2,   //IDC_OPCDATACTRL1
                    "{FECBB6D0-6378-4B3E-A0EC-DCB28655BB55}",WS_TABSTOP,131,
                    112,17,17
    EDITTEXT        IDC_EDIT1,95,54,81,16,ES_AUTOHSCROLL | NOT WS_TABSTOP,
                    WS_EX_RIGHT
    PUSHBUTTON      "Disconnect",IDC_BUTTON1,151,84,61,22
    PUSHBUTTON      "ConnectObject",IDC_BUTTON2,68,84,71,21
    LTEXT           "This example uses the ConnectObject method to setup a subscription read and get the data back in the ValueChanged() event of the OPC data control and then update the text box below.  This is all done programmatically in the code in this example. ",
                    IDC_STATIC,7,7,258,38
END

void CConnectObjectDlg::DoDataExchange(CDataExchange* pDX)
{
    CDialog::DoDataExchange(pDX);
    //{{AFX_DATA_MAP(CConnectObjectDlg)
    DDX_Control(pDX, IDC_EDIT1, m_EditControl);
    DDX_Control(pDX, IDC_OPCDATACTRL2 , m_OPCDataControl);
    //}}AFX_DATA_MAP
}

----------------------------------------------------------------------------

Can anyone kindly explain what is the meaning of IDC_OPCDATACTRL2 in both parts and also what is the meaning of the CONTROL part in the first part written in rc file?

Thanks ahead!