circuit simulation is a computer assisted method used to simulate the behavior of a circuit in a virtual environment (no need to create real circuit and blow up tranzistors :grin: ), based on mathematical computations ... software ex: Orcad
Pcb designing ... that's when you want to go to real ... In order to make the cooper board to solder the electronic components on it, at the begining, you need to draw the connections existing between each component's terminal according to the electrical schematic of the circuit, and of course the pad for each terminal needs to be drawn in order to drill holes later in that place for the component terminal ... when ready, you have 1 layer. You need to transfer somehow the drawing (from computer or paper) on the cooper board. In order to draw correctly , you need to know/approximate the distance between terminals and component dimensions , when using computer programs like Eagle , this dimensions are already included in the software in the form of library's based on the component datasheets, you just need to select the correct pattern for your component.
For double sided cooper boards you can make 2 drawings for each side, so you have 2 layers. You can't build multiple layered (>2) board's at home . (for exemple a cell phone's pcb can have >7 layers....)