A DNS server manages name resolution of computers on a subdomain. For example, going to docs.cslabs.clarkson.edu you are using clarkson.edu's DNS server to find the ip address of cslabs. This would be the CSLabs' DNS server. Now we use the CSLabs' DNS server to find the ip address of docs.
Where are the files?
The files you need to edit are in /var/named/. They link to corresponding files in /var/named/chroot/var/named/. You need to be root to edit these files.