Resolver
A DNS Resolver is part of a DNS server. It navigates the DNS tree to find any available DNS data.
Stub Resolver
A Stub Resolver is part of a DNS lookup system on devices. It stores IP addresses to iterative resolvers.
Responses are placed in the resolver cache. The data remains cached according to Time-To-Live.
Iterative Resolver
An Iterative Resolver is part of a DNS server. It navigates the DNS tree to find any available DNS data in order to determine which domain name resolves into what particular IP address.
The resolve process is done through iteration. The resolver starts from the top - the root domain, and works its way through the DNS tree until it receives an answer.
All data received during a query is placed in the resolver cache. The data remains cached according to Time-To-Live.