A hub or switch is basically a box that your lengths of UTP plug into. It is necessary for more than two computers. The difference between a hub and a switch is that whilst a hub sends data to every single computer on the network, a switch only sends data to the machines that require it. The result of this is that the network can run in full duplex (200mbit/sec) and the pings are better for multiplayer games- especially at a large LAN party where there could be several games going on and an FTP server all on the same network. With a hub, the games would become unplayable if people access the FTP server but with a hub, the pings are still very respectable. Since
switches are a lot more expensive than hubs, I will be concentrating on hubs.