AFX is an abbreviation for a group. The MFC group was originally called the "application Framework group" during the inception of MFC. However, X doesn’t stand for anything other than sounding cool. The original AFX group was renamed to MFC long ago. There is no current AFX group. But the "AFX" hasn’t been changed to "MFC" for the compatibility.
另外有一說法是,X 代表微軟開發Application Framework的眾多開發人員。
這個宏是MFC用來構造訊息映射表時用到的輔助宏,它埋在類識別宏或動態識別宏中