Can I connect 2 desktops & a laptop to wireless router? BUT...?

Yes you can do this. Normally when you look at a wireless router, on the back there are some RJ-45 female connectors, along with one that lets Internet in. You can hook other computers up to the router and still have a wireless laptop connect to it. But aside from a laptop being hooked up to it, there is a large range of things that can connect. Such as a PlayStation Portable (PSP), or a cell phone with WiFi capabilities. Basically anything with WiFi capabilities.