Located at /etc/resolv.conf, this file defines your search domains and your DNS servers. You probably don't want more than 4 to 6 search domains and you cannot have more than three DNS servers listed. The format is:
domain freebsdwiki.net nameserver 169.254.1.1 nameserver 172.16.1.1
To attempt to resolve incompletely qualified hostnames using more than one domain name if necessary, use:
search freebsdwiki.net somethingelse.com anotherdomain.org
In plain english, that line means that if you try to ping webserver from the shell, your machine will try to resolve webserver.freebsdwiki.net, webserver.somethingelse.com, and webserver.anotherdomain.org before giving up.
Be careful with this, you really don't want to have every attempt at a DNS resolution take 15 seconds or more to time out because you have to contact tons of different nameservers due to your "search" string. There is also a pretty obvious potential for namespace overlap and confusion, ie if you have distinct hosts named webserver, fileserver, or printserver (or whatever) in more than one of your search domains.