I am having trouble understanding the definition of a "single-sided" printed circuit board (PCB). Here are the situations I am confused about.
Through hole components on the top layer only and traces on the bottom layer only.
Both the through hole components and traces are on top layer only.
Traces on both the top layer and the bottom layers and the through hole components only on the top layer.
I have been assuming that only numbers 1 and 2 above are considered "single-sided" because the traces are only on one side of the board. Am I mistaken?
Does the concept of "single-sided" or "double-sided" refer to the placement of the traces only?
In addition, does "single-sided" mean "one-layer"? Are these synonymous terms?
Lastly, could someone explain the distinction between the use of the word "layer" in the above context and in the context of the Eagle software in which there are many "layers" in the PCB layout editor?