I would like to understand the need for ServerName in apache.
Lets say that I have a web site with IP 12.13.14.15.
In DNS zone I call it example.com and refer the Ip to it with an A record.
Why isn't this enough? It tells the www that whenever anyone writes example.com, it needs to go to 12.13.14.15 ip.
So why do I need to set it also in apache with NameServer attribute?