A switch is similar to a hub, except that it registers the IP addresses of the computers plugged into it. When it receives a message, it only sends it to the intended recipient. Switches cut down on unnecessary traffic broadcasts and allow you to have an affordable high-performance network.
Switches are used to connect computers on the same network; they do not provide Internet access. You can still share your Internet connection through ICS, but performance issues and bottlenecks may arise. The USRobotics 10/100 Ethernet Switch has auto-crossover cable detection on each port, so you only need one kind of cable to make it easier to get your network up and running.
You may also be able to plug your switch into your broadband modem, but only if you get multiple IP addresses from your provider. This usually costs more. For increased performance and functionality, you need a router.