Stacking:
Stacking is what layer is on top of another layer. It is the Z-index number of the layer. 1 being the lowest in the stack or bottom and the proceeding higher numbers stacking on top of each other in a progressive order.
To adjust Z-index:
a. you can change the number in the Layers Panel by clicking in the "Z" column next to the layer and typing in a new number.
or
b. You can select the layer and enter a Z-Index number in the "Z" text field in the Properties Inspector.
