类型库,接口类,调度接口,一般接口有什么区别?(100分)

interface

uses Windows, ActiveX, Classes, Graphics, OleCtrls, StdVCL;
// *********************************************************************//
const
LIBID_Memo: TGUID = '{55E49D30-9FFE-11D0-8095-0020AF74DE39}';
IID_IMemoApp: TGUID = '{55E49D31-9FFE-11D0-8095-0020AF74DE39}';
CLASS_MemoApp: TGUID = '{F7FF4880-200D-11CF-BD2F-0020AF0E5B81}';
IID_IMemoDoc: TGUID = '{55E49D34-9FFE-11D0-8095-0020AF74DE39}';
CLASS_MemoDoc: TGUID = '{55E49D35-9FFE-11D0-8095-0020AF74DE39}';
type
以上LIBID_xxxx,class_xxxx,diid_xxxx,iid_xxxx有什么区别,什么时候该什么?
// *********************************************************************//
// Forward declaration of interfaces defined in Type Library //
// *********************************************************************//
IMemoApp = interface;
IMemoAppDisp = dispinterface;
IMemoDoc = interface;
IMemoDocDisp = dispinterface;
}';
IMemoApp = interface;
IMemoAppDisp = dispinterface;
.......
........
是什么意思?有什么作用?

IMemoApp = interface; IMemoApp是一个接口。
IMemoAppDisp = dispinterface IMemoAppDisp是一个调度接口，二者的GUID相同，可以用IMemoAppDisp来在另一程序中调用上面的接口。
有了IMemoAppDisp，可以用Variant方式后期绑定调用。