The resolver 1) or recursive resolver is a method (class/interface) that:
They must be able to access at least one name server and use that name server's information to answer a query directly, or pursue the query using referrals to other name servers.
A resolver is typically directly accessible to user programs; hence no protocol is necessary between the resolver and the user program.
Resolver is also another name for a nameserver that can handles recursive queries.
The resolver starts from the root and goes all the way down to find the authoritative nameserver of the name.
Example: when a user asks the website dns name datacadamia.com, the web browser performs a query with the resolver.