"<FONT color=#000000>Buy a router and a wireless pc card then you'll be set..."
No you won't. You'll have a worthless client device unless it has a wired NIC in it. A router is not an AP. A combo unit is a an AP integrated with a router. They are not the same thing however.
An Access Point is it's own device. AP's were around long before they started integrating them with NAT routers. It was and is a good idea to combine them but they are not interchangeable. An AP can either attach to your LAN as a node, similar to a hub, but it will communicate to it's associated clients via microwaves vs copper cabling. You don't have to have the AP attached to the LAN. You can have a small contained lan with just the AP and some clients. Microwave bridges connect remote LAN's transparantly connecting the second site to the first. Building to building and so forth. They can be point to point, two bridges, or point to multipoint, one parent bridge and two or more child bridges. </FONT>