dig requests to a dns server it's list of ips mapped to urls. The dns server asks the bind service for it to indicate the correct file zone where the requested urls are located. Here's how to configure bind and here's how to configure a dns zone.
> dig @126.96.36.199 any
> dig www.google.com any
In this case, dig will first query my ip provider's dns server for the ip associated to the url "www.google.com" and only after it will dig for the ip's mapped by the "www.google.com"'s dns server.
> dig -x "ip"