Network cards? - I'm lost

[fbd]

last november, we networked our computers at home. 3 of them, 2 desktops and a laptop. there might be other ways, but what we did was buy a router, hooked it up to the cable modem, put cable ports in the three rooms, and hook up the network. the computers are all basically right above each other. as far as i know, though, you either need a network or two cable modems to be online on 2 computers with one connection