I am guessing you want to share your cable modem connection. I just set up a small 2 PC network for my friend with the LinkSys 4-port cable/dsl router. It went together really easily. You plug the cable modem into one side of the router(I think the port is labeled "WAN" if I recall correctly) and then plug your PCs into the line of ports on the back of the router that are used for the PCs...it is easy to do. You configure the router through your browser using an IP address that is in the manual. Make sure you get all the info you need though. Your host/domain. If you have something like @home it should all be on the sheet they gave you when you signed up...the sheet with your password and so on. If you lost it, you can call them. So you'll need your host/domain, fixed IP address, Gateway IP, subnet mask, DNS servers, and DHCP server. Your ISP will tell you all of this if you call them. Other then that you'll be all set as long as you have NICs and CAT5 patch cord.
I just realized I didnt even answer your questions totally. I router is essentially a smart hub...or, a better way to put it is...if you were to breed a hub with a switch you'd have a beautiful baby router. The main advantages are, the hub acts as a hardware firewall and it also lets you, as I explained above, share one cable connection. Hope all of this helps.
good luck,
-doug