Flash高手请进

能解释下，这个是什么意思吗？

captionFN = function (showCaption, captionText, bName) { 
 if (showCaption) { 
  _root.createEmptyMovieClip("hoverCaption", this.getNextHighestDepth()); 
  cap.desc.text = captionText; 
  cap._width = 7*cap.desc.text.length; 
  cap._alpha = 75; 
  //  
  if ((bName._width+bName._x+cap._width)>Stage.width) { 
   xo = -2-cap._width; 
   yo = -17; 
  } else { 
   xo = 2; 
   yo = -17; 
  } 
  hoverCaption.onEnterFrame = function() { 
   cap._x = _root._xmouse+xo; 
   cap._y = _root._ymouse+yo; 
   cap._visible = true; 
  }; 
 } else { 
  delete hoverCaption.onEnterFrame; 
  cap._visible = false; 
 } 
};