What is the layer above/below in a NN?
Normally we imagine a neural network propagating from left (input) to right (output), but what is the layer above/below the current layer? Is the input the bottom layer or the top layer?


Yes, a "below" layer means an "earlier" layer, i.e. closer to the input. For CNNs it is quite common to speak of lower layers, lower level feature maps etc. 

And for RNNs you can even take this literally as they are usually visualized bottom-to-top instead of left-to-right (e.g. see figures here).