Greetings

I would like to setup a server that is for in house use only. This is
not for outside use.

So I'm trying to understand what is a good way to setup the hostname
for the server.
Do I use localhost?
Do I use example.com?

Is there some other way to refer to something like a communication/info server?
   For this thinking maybe something like using the lan NAT address
for the machine.

I'm not even sure I'm asking the question 'right' and the 'web' is
being singularly unhelpful!

TIA