Domain Name Servers (DNS) is an internet service that translates domain names into IP addresses. They take a user-friendly domain name (such as fullmedia.com) and turn it into an IP address (like 18.104.22.168). You can really think of a DNS as a big phone book.
Typically when you purchase your domain name from an authorized seller (for example, GoDaddy), you set up an account to purchase this domain name. Usually, this account is where you can control your DNS information, and is what Full Media uses to make websites appear live on the internet.
In case this information is not readily available, there are also a number of tools you can use on the internet to help figure out where your DNS information is. MX Toolbox (http://mxtoolbox.com/) is a great resource to help get this information.