Multiple web sites, one IP address...

I have a question that I'm not sure how to phrase (and google)... I know this is a little off-topic, but I was hoping some guru here might at least be able to point me in the right direction... --- I have several web sites (PHP-driven :-) that I want to host on my new xServe, which is sitting behind a regular router/firewall. I know how to forward port 80, etc., from the WAN side to the xServe on the LAN, and that's working fine. But now I would like to move several web sites that are presenting running on various ISPs to this server o' mine. This is where I'm kinda stuck. I know the xServe and Mac OS X Server can run multiple web sites/domains (the docs say so). But does each of my domains, registered with Network Solutions, need to point to a unique IP address? If they can all point to the same IP address (my router), then once the HTTP request is passed through the router, and port-forwarded to the xServe, how will the xServe know which request is for which domain/web site? If each domain needs its own IP address, then how can the all be forwarded to the same single router (which just has one IP address)? --- Asking this question I realize that there is some fundamental network stuff I don't understand. But the thing is, I don't know *what* I need to learn or in what order, so it's a little hard to start googling my ignorance away. If any of you know a good tutorial or how-to guide that more or less covers this kind of thing, I would very much appreciate it. ...Rene ...René --- René Fournier www.renefournier.com