localToGlobal question

Hi
After multiple tests I’ve finally made localToGlobal() work the way I want it to work, I still have some questions though:
let’s say on the stage I have mc1 at (50,50), inside mc1 there’s mc2 at (50,50) and inside mc2 there’s mc3 at (50,50)
so mc3 inside mc2 inside mc1 on the stage, each one at (50,50)

now I want to know mc3’s coordinates on the stage:
var pt: Point= new Point(mc1.mc2.mc3.x, mc1.mc2.mc3.y)
mc1.mc2.localToGlobal(pt)

which displays (150,150), perfect
what I’m wondering is, what do these do?
mc1.localToGlobal(pt)
and
stage.localToGlobal(pt)

I’m a little bit confused since the correct way of getting a mc’s coordinates on the stage is apparently mc.parent.localToGlobal(mcPointObj)

thanks