What is an NIC? Help!

I've just moved house, and our lovely landlord hasn't provided us with a phoneline. So I was looking at the telewest blueyonder broadband website and they say that with an apple computer you have to have an NIC, or network interface card. What is that? Is it the same as an ethernet port? I've got an iBook G3 with dual USB, dial up, firewire and ethernet ports. Surely the cable modem will work with one of those! Last time we had a wireless setup, but there's no point taking that route since I'll be the only one using the line this time.
Help me, I need my internet!

Suz