Say you have a domain connected to just one site or application and this site is hosted on a server on your internal net.
This server address is then nat’ed in you firewall from an external address to an internal host.
If this is the case you probably want to redirect the dns lookups for the host to stay within your internal net.
If it would have been in the form of host.domain.tld things would have been simpler.
Turns out it is not that complicated to redirect just example.tld either..
Just add your domain as the host and the tld as domain and you are good to go!