A Single-Sided Printed Circuit Board (PCB) is a type of circuit board that has conductive traces, components, and pads on only one side of the board.
A Double-Sided Printed Circuit Board (PCB) is a type of circuit board that has conductive traces, components, and pads on both sides of the board.
Multilayer PCB (Printed Circuit Board) design is a type of PCB that consists of more than two conductive layers sandwiched between insulating layers.