A network port is a "channel" for information received over the network. Your computer has physical ports, where a wire is plugged in (or a wireless connection by radio in many cases), but this port is not the same thing as a port being referenced by software. From the perspective of software a network port is the location of a stream of data made available to the software by the operating system. The operating system takes the data coming in to the physical port and divides it up into thousands of different virtual locations that can be used by all the different software running on the system.