As explained under point 4, the PCB is defined as a number of copper layers in a well defined sequence. Copper layers of a PCB are usually just named layers or also called SIGNAL layer. However to define the complete PCB, other layers are required. They are usually named by their functionality and position. Examples: TOP solder mask layer, TOP paste layer, TOP legend layer, BOTTOM peel-off layer etc…
In general a PCB is classified by the number of copper layers. Boards that consists of 1 or 2 layers are often called:
- 1-layer PCB = single sided PCB
- 2-layer PCB = double sided PCB
Boards with no copper layers or with more than 2 copper layers are defined and called by the number of copper layers.