apache

[Joshua Holland]

I'm trying to learn apache.  When I run it I get
'Apache: Cannot determine local hostname'
Does the hostname have to be set up with my service provider or something?
I set the ServerName directive to my hostname.domain.com (hostname is what's in my /etc/hostname file, and I have a domain name set up).
Are there certain criteria for what the hostname in /etc/hostname can be?
And what is /etc/hosts?
Help please.

Thank you.