Switches are devices that will allow you to connect a number of computers together. They can also be used for receiving a number of wireless connections.
Switches that consumers use usually have four ports (or outlets) to plug network wires in from PCs. Commercial switches will have 8, 16, 20 or even up to 48 ports.
You will often find that the router is combined with a switch, which is what you really get when you buy a DSL modem/router or cable modem/router.
Switches are also made for other media than network (Ethernet/CAT5/6) cables. You can get switches that connect USB cables together.
Hubs are similar to switches. Hubs also allow you to hook a number of cables together. However, hubs are dumb and all traffic goes out all ports. If you gave a choice of a hub or a switch, you want to get a switch. A switch will run faster than a hub since traffic is limited to what belongs to that device. Networks that still have hubs (hubs were the way to connect networks together until soon after 2000) can be significantly sped up by just replacing a hub with a switch.
Send your questions to Dwight Watt at email@example.com. He teaches at a technical college in northwest Georgia and does consulting work for businesses and individuals. His website is www.dwightwatt.com.