If you have a wireless router, then you can connect multiple computers "wirelessly", that is, "without wires", if they have "wireless" network cards. They replace the "wire" with an "antenna".
Just busting your chops a bit, but yea, you can create a wireless network just like any wired network if you have a wireless router and each computer you want to hook up has a wireless network card. You can still hook up some of the computers with wires too, since that results in a faster and more reliable connection. You just have to get the right wireless network card for each computer you want to connect wirelessly.
A tip - buy wireless cards from the same company as the router. If you use a d-link router, get d-link wireless network cards. Same goes for linksys, netgear, etc. Each company has proprietary extensions to the wireless protocol that makes it's routers work best with their own network cards, so you can usually get a little better connection if you use all the same brand wireless gear.
Make SURE you encrypt your wireless network using WPA encryption immediately upon setup and change the router password before you even hook it up to the internet. If you don't, you're pretty much inviting anyone with a wireless network card to enter your network and mess around with your computers.
