Computer motherboard and fan. The fan (upper centre) is used to cool the heat sink (below fan), which in turn absorbs the heat generated by the computer's CPU (central processing unit, below heat sink). The other components are part of the motherboard, the computer's central set of circuits and electronic components. The components and the CPU are all fixed to a printed circuit board (PCB). Some of the printed circuitry (gold and yellow) is seen below the components.