Windows 7: How are ports used? How can I use them in my home network?

I've studied ports before while pursuing my undergraduate degree. However, the course was very broad and covered many fields of networking. I still do not understand how ports are used. What are some typical uses of them, especially in a home network?

Hardware ports: http://en.wikipedia.org/wiki/Computer_port_(hardware)
Networking ports: http://en.wikipedia.org/wiki/Computer_port_(software)