What does a modem and a router do?

My modem only has a usb open. i have a wifi ready laptop. what do i need to surf on my LT? WAP or ROUTER?

• my roomate has a cable modem and is connected to his computer through the ethernet port. there is another usb port on the modem and the cable modem instructions are very clear that two computers can be simultaneously connected and used one by usb one by ethernet. He wants to be remain connected directly to the cable modem via ethernet for more reliable downloading. i only need to have a wireless signal available in order to surf the net on my wifi laptop. What exactly do I need? I bought a Linksyswirleess G router, but since it must be connected to the cable modem only by ethernet, i cannot use it. So i think i need a device that can be connected to the modem via usb. do i need a router or simply a wap? are either of these available for only USB connection??? Please help, i am living in South America and it is very hard to communicte such specific computer needs here! Thanks.

• Answer:

  If you already bought a wireless router, then you should have your friend switch out the router he currently uses with that one. It will allow him to still connect directly to the router with an ethernet cable, as well as allow you to connect wirelessly. Then all you would need would be a wireless receiver card.