In practice, port use looks something like this: imagine a server is running an FTP server and a web server simultaneously. Ports are the solution to this issue, allowing multiple processes and activities to have access to a shared network interface. The issue with this is usually devices only have a single network interface. Your hardware is constantly managing multiple activities and tasks at once, and many of these will require network access. These gateways exist in the network and can be points of vulnerability.

You might describe ports as gates into your hardware.