Imagine a street with a bunch of houses on it. The street is analogous to a single input line the brings in internet and mail data. The houses are individual elements, e.g. computers, laser printers, any ethernet device, etc. Incoming data has a header that says where this data should go, that is what is the address to which the data should be delivered.The router dissects the incoming data and dtermines the address and then routes the data to the appropriate device.
For example, I have two computers, mine and my wife's, plus a laser printer all connected to a router. Each of us has a different e-mail address so that e-mails addressed to me are routed to my system. The laser printer also is routed to our computers so that when a "Print" command is issued, the print data is routed to the laser printer.
A hub, as Kelly pinted out above is a "dumb" device that just connects all the components together.000
MamaMoose