The audio input and audio output ports on a Windows PC. On Windows desktop computers, the ports are generally color coded and often support a surround sound system. In contrast, a Mac does not have color-coded ports and generally has one or two 3.5mm ports. See
PC input/output.
PC Audio Ports
This is an example of surround sound support on a Windows PC. If only a single set of speakers are used, they are plugged into the green output port.