DNS is a networked database system that's used for sharing machine names and IP addresses across the network.

On the main screen, you can configure the domains that you want to search for names in and the servers where you get your DNS information from. These can both contain multiple entries; if, for example, you wished to be able to telnet to machines in both pell.chi.il.us and pell.local domains, you'd add both these domains into the domains list -- then you'd be able to telnet to gehenna.pell.chi.il.us by telnet gehenna, and to webshield.pell.local by telnet webshield.

If you press the [OPTIONS] button, another screen will come up that lets you set various optional DNS.

ndots
Set the number of dots that must appear in a filename before the name resolver adds your domains to it. ndots defaults to 1, which means that any name containing a dot will not be looked up inside any of your domains. If you have a complicated domain containing multiple levels of subdomain, you might want to set this to something else (for example, if you are in the pell.chi.il.us domain, but that domain has the two subdomains pdx and lisle, setting ndots to 2 will allow the resolver to search for pell.pdx and tsfr.lisle as pell.pdx.pell.chi.il.us and tsfr.lisle.pell.chi.il.us.
resolver debugging
sets RES_DEBUG in the resolver options. For further information, you will need to look at the online manual pages for named.
search order
Sets the system search order. The default is hosts,bind, which means look in the system /etc/hosts file, then query DNS for the name. You can change it to use the hosts file, DNS (bind is the name that the system uses), or NIS services.
sort list
This is used to sort the results of a name lookup by IP address. A sortlist is a list of network addresses (optionally followed by / and a netmask), and this will be applied to any results so that the results will attempt to follow the sortlist.