PCB in electronics context Stands for “Printed Circuit Board” which is a thin board made of FR-4, fiberglass, composite epoxy, or other laminate material according to the required field of application. Conductive paths (tracks, wires) are etched or printed onto board, connecting different signals from components on the PCB, such as resistors, digital integrated circuits, capacitors etc. The components (SMT or through-hole) are mounted or placed directly onto the surface of printed circuit boards using solder.
PCBs are used in almost any electrical devices like smart phones, computers, cameras, embedded controllers and toys. They hold electrical components together both electrically and mechanically.
Most PCBs are green because of the coating called solder mask applied in order to insulate and protect the copper layer from oxidation, humidity, and to bridging traces during soldering. The green is most used color and it is almost industry standard color for solder mask but you can see other colors too.