See the links below that I found by typing "Router vs switch" into Google:
What is the difference between a router and hub or switch?
General Networking/Lan/Wan - Router versus Switch
You can also use both depending on the network needs.. As an example, for the last two days, I've been laying the wires for and configuring a small office DSL network which uses a standard Verizon wireless router/modem combo which contains a 4 port switch, all in one unit, and it connects directly to the ISP.. Next in line, one of the router ports is then used to connect to a plain D-link 8 port switch about 40 feet away where a couple more wired computers are then connected.
Hope this helps.
What is the difference between a desktop switch and a router? Why would I choose one or the other? I want to be able to connect several pc's to the internet through one dsl connection at the same time.