One popular practice is to assign an IP number (or more than one) to a domain itself. For example, many sysadmins will assign the same IP number to the Web server of a domain and to the domain itself. This allows one to browse your domain's website with http://www.domain.com or simply http://domain.com.
Linuxconf allows you to set the default IPs of the domain right here. If you do so, it will enter the proper records in the DNS, but it won't modify the reverse mappings of the IP numbers. This means that two following commands, for example:
nslookup domain.com nslookup www.domain.com
will produce the same result (the same IP numbers). But if one types
one will get www.domain.com as the result and not simply domain.com.