For the digital part, front-end design refers to the stage from circuit description to function simulation, synthesis and then to timing simulation. For the simulation part, it refers to the stage of completing the creation of the library, the description of the circuit, the simulation of the circuit, and the generation of the electric network table.
The back-end design is the stage of layout and layout, chip testing, etc.
PCB is a product that puts various electronic components on a copper coated plate to become a system, and layout generally refers to the back end of IC design, that is, layout design.