In the following code we use target in the function:

moon.mouseEnabled = false;
sky0.addChild(moon);

addEventListener(MouseEvent.MOUSE_DOWN, onDrag, false, 0, true);
addEventListener(MouseEvent.MOUSE_UP, onDrop, false, 0, true);

function onDrag(evt:MouseEvent):void {
    evt.target.addChild(moon);
    evt.target.startDrag();
}

function onDrop(evt:MouseEvent):void {
    stopDrag();
}

But if I rewrite this code without evt.target it still work. So what is the difference, am I going to get errors later in the run time because I didn't put target? If not then why some use target a lot while it works without it.

function onDrag(evt:MouseEvent):void {
    addChild(moon);
    startDrag();
}