I am going through MS training kit  ..i have come across the following practice  ..
Installed Windows Server 2008 R2 on a physical or virtual computer, which should be
named SERVER11 and should be a stand-alone server. This computer hosts the DNS Server
role and the Active Directory Domain Services role that you install and create through the
exercises in this chapter. Assign an IPv4 address from one of the private ranges, such as
192.168.x.x, and map its DNS server address to the address you assigned to SERVER10.
what does it mean 
 MAPPING IT DNS SERVER ADDRESS TO THE ADDRESS YOUR ASSIGNED TO SERVER10