[Solved] pcb stackup question

[Lucky-Luka]

Hi
In Learning Altium essential ed2 there is a 6 layer pcb stackup.
I haven't understood with what logic the nets were divided on the various layers.
Are layer 2 and 5 without nets? They are called planes while the other layers are called signal.
If they are empty why are they present?
Thanks

[robertferanec]

Layers 2 and 5 are used as solid GND planes. Then, L4 will be used for Power and L3 will be used for noisy signals, feedback and a few more. It will be explained.