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).