rptGuestbook.DataSource = Cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection)

Hi experts ...
this code is used to select records from Access db table.
i need to understand the meaning of these two lines :
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rptGuestbook.DataSource = Cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection)
rptGuestbook.DataBind()
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This is the whole code :

<script language="VB" runat="server">
Sub Page_Load (Source As Object, E as EventArgs)
      Dim strConn as string = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & server.mappath("guestbook.mdb") & ";"
      Dim MySQL as string = "SELECT Name, EMail, URL, Comment FROM Guestbook"
      Dim MyConn as New OleDBConnection (strConn)
      Dim Cmd as New OleDBCommand (MySQL, MyConn)
      MyConn.Open ()
      rptGuestbook.DataSource = Cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection)
      rptGuestbook.DataBind()
End Sub

</script>