Differential Signaling is a method for transmitting one signal using two signal lines. This method uses voltage differences between two signal lines, so any noise on these lines can be cancelled. The pin layout needed to do this would be ground-signal-signal-ground, where the ground pins are used to prevent interference with other adjacent signal pairs. The differential signaling method is more resistant to noise, and therefore able to transmit data at a higher speed. That being said, the drawback is that it takes additional pins in order to transfer the signal. Impedance matching is the ability to keep the resistance level consistent during high frequency signal transfer. In order to achieve a higher quality signal during high-speed transmission, the impedance level of the circuit including that of any connectors should be matched. Without Impedance matching, the signal is reflected and does not flow smoothly.