Think of it as an old style telephone line coming into a small town, and everyone is on the same party line, so everyone hears all rings and can listen to all calls.
I only answer/respond to calls with 1 ring, you only answer calls with two rings, etc.
If a signal is sent out on the network cable, and it has your machine address (ip address) on it, your machine will responed. This is like the family the caller wishes to reach. If the servers are running, apache server will respond if it sees "port 80" in the network signal. FTP will answer if it sees "port 29" and so on for all the other services that may be running. This is like the member of the family (husband, wife, children) the caller wants to talk to.
This is to be distinguished from the hardware devices on your computer, such as the serial port, printer port, usb port etc. Same word, different meaning. It would be better to refer to 'printer connector" and 'serial connector"
Does this help?