The OSI model organizes networks in layers. Each layer communicates via an interface with the layer "above" it and with the layer "below" it. A layer is unaware of anything beyond those two neighboring layers, which helps greatly simplify things.
Last Sunday at the Cluny museum I saw the tapestries of the licorn and their description of the five senses. I experience the world around me, that communicates with me via the interface of my five senses. I communicate back via talking, writing, and otherwise expressing myself. My internal (conscious) state is a layer, the outside world around me is another layer. If Freud was still in vogue, I would say that my internal conscious state also has an interface with my subconscious, that would be another layer underneath it, or that there is a small voice in my heart that could be heard when all is still. If one took science-fiction seriously, we could also say that there is a world beyond the one that we experience with our senses, or make all sorts of wild conjectures. But the only layers that have a hope of being accessible to our minds are the one immediately above and the one immediately below it - the physical world, and the world of the unconscious.