Touch.AbsoluteX is the same as Touch.AbsoluteXAt(0).
Touch.AbsoluteX just does not take an index as parameter, and is always about index zero. (index in the list of touches)
Since 'Absolute' (in this case) means position on the canvas, with x=zero and y=zero at left-up your SCREEN, it can not take the "layer" as parameter.
TouchID is an expression (a number) that identificates roughly a 'gesture'.
If you use 'on any touch', that expression holds a number corresponding with all the touches that are on that moment on screen. So, everywhere you see 'id' like in 'Touch.AbsoluteYForID(ID)' .... that ID is a number retrieved and stored with the TouchID expression.
I think that most people get the x/y coordinates from a HUD layer with no parallax when they want absolute x/y coordinates. After all thats kinda the same.
Now, wherever you see 'Get ..... coordinate in the layout (with x=zero and y=zero at the zero points in the layout) you can specify a "layer" in the parameters. And this absolutely necessary.
Consider this example:
https://www.dropbox.com/s/bxnfx9snt60j9 ... .capx?dl=0
I have a rotating layer with parallax. When i fire bullets at touch.x,touch.y (layout coordinates) ... then the bullets are not going direction the touch position. That is because the layer with the turrets is (with its own coordinates) moving inside the layout.
To fix this, we need the layout parameter.
https://www.dropbox.com/s/gn013jr7lwvki ... .capx?dl=0
Surely hope i helped you some.