[Techtalk] "virtual" DNS resolution?

[Cari]

Hi LinuxChix,

Right now, DNS is pointing to my home router/firewall (my one IP 
address).  From there, my NAT router routes certain ports to my linux 
box.  What I would like to do is make it so that I have "virtual" 
hostnames...  So that if I point to www.domain.com or mail.domain.com 
then it will go to the one linux box.  

My guess is that I have to configure DNS to run on my box, open 
up/redirect the port(s) on my router, and then set it up so that 
www.domain.com points to the same IP as a few others.  Is that right?  
Are there any special considerations because the internal machine is 
using an internal IP?  I understand only the basic concepts of DNS, 
mostly from the user's perspective, so I'm a little bit perplexed.   Can 
anyone help me out here?  Know any good links or have wisdom you can 
spare? 

I'm doing this mostly to learn, and it's fun every time I triumph over 
the machine.  I doubt I will ever run out of things to learn with this 
new linux hobby!   Thanks...

Thanks!
-- Cari