system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is a network port?

I've always seen it on some devices and games (like terraria) where you specifically have to configure the port too so that you can successfully connect a server. But never truly understood what it was.

Similarly I never understood wether a port is represented by data inside the computer that associates something to something or if for every port there is a specific cable/wire that transmits only the information from that port or if a port is just a medium of input in the computer.
gpt
Think of it like a big building with many apartments. The building has a street address. That is basically equivalent to the IP address of your computer.

But since there can be many tenants (services) in the same building, you also need to know the apartment number.

More technical explanation: Many services (e.g. email server, web server, file server, print server, etc.) can be running on the same computer, sharing the same network interface and therefore the same IP address.

To keep those apart, each service is listening on a different port (e.g. \`25\` for email, \`80\` for web server, etc.). When you send a TCP/IP message, you have to specify the recipients IP address, but also the port on which the message is to be received.

Ports are a logical concept. They physically use the same cable as all other messages. It's just an additional number encoded in the TCP/IP package. When your operating systems network stack receives such a message, it will read the port number and forward the message to whichever service (tenant) is currently holding that port.