How Forwarder works...

How DNS resolves DNS query using "Forwarder"???

A DNS server configured to use a forwarder will behave differently than a DNS server that is not configured to use a forwarder. A DNS server configured to use a forwarder behaves as follows:

1. When the DNS server receives a query, it attempts to resolve this query using the primary and secondary zones that it hosts and its cache.
   
2. If the query cannot be resolved using this local data, then it will forward the query to the DNS server designated as a forwarder.
   
3. The DNS server will wait briefly for an answer from the forwarder before attempting to contact the DNS servers specified in its root hints.
   

When a DNS server forwards a query to a forwarder it sends a recursive query to the forwarder. This is different than the iterative query that a DNS server will send to an other DNS server during standard name resolution (name resolution that does not involve a forwarder).

Query using Root hints vs forwarder

Using Root hints

Root hints are DNS resource records stored on a DNS server that list the IP addresses for the DNS root servers

Using Forwarders

A forwarder is a DNS server designated by other internal DNS servers to forward queries for resolving external or offsite DNS domain names

DNS Lookup Query