Paint System allow you to do operations on your layers.
This will convert any layer into an image layer, so they can be painted.
This includes

This will copy the layer(s) to internal clipboard.
This will paste the layer(s) to internal clipboard.
This will only paste the layer type, and will not save the attributes of the copied layer.
This will paste the layer(s) to internal clipboard with all settings linked to the original.
This allows for different objects to use the same layer.
Eg. Gradient layers can affect multiple objects (great for 2d looking gradients)
ADJUSTMENTGRADIENT