MSDN中说的非常详细啊。CWnd就是你点击鼠标时的窗口指针啊，Point就是鼠标点击时的相对于屏幕的坐标。pWndHandle to the window in which the user right clicked the mouse. This can be a child window of the window receiving the message. For more information about processing this message, see the Res section.pos Position of the cursor, in screen coordinates, at the time of the mouse click.
point 是鼠标按下时的坐标，也就是菜单弹出的位置。