Basic Multiple Computer Interconnect with Ethernet

May be needed for separate functions, or simply because the cable distance is too long for a video cable

Devices "star" wire, typically with a cable distance up to 328 feet/100 meters, on Category 5 or better cable

The switch acts as an interconnection point for the various computers. It allows simultaneous communications between pairs of computers, or even broadcasts to multiple computers.

Ethernet, which comes in speed from 10 million bits per second (10 Mbps) to 10 billion bits per second (10 Gbps) is intended for interconnecting computers.

Most commercial computers will come with a single 10/100 Mbps Ethernet (also known as IEEE 802.3) connector.

If you only have two interconnected computers, you can use a "crossover cable" and omit the switch.  Small switches, however, are inexpensive

The presence of Ethernet in no way prevents the computers from using serial, USB, or other computer peripheral interfaces.
In some cases, NMEA 0183 or NMEA 2000 devices can be connected to Ethernet by an interface converter/multiplexer.

You can create logical groupings of different functions with Ethernet, extend the cable distance, or share an Internet connection
Ethernet also provides a way to have very minimal computer functions elsewhere on the boat