The PowerDNS server daemon is a versatile nameserver which supports a large number of backends. These backends can either be plain zonefiles or be more dynamic in nature. Additionally, through use of clever programming and caching techniques, PowerDNS offers very high domain resolution performance.
Prime examples of backends include relational databases, but also (geographical) loadbalancing and failover algorithms.
The PowerDNS recursor daemon which is also part of the PowerDNS compilation is a dedicated high performance recursive (aka caching-only) Nameserver that already powers some larger broadband ISPs and as of late learned to embed Lua Scripts making it possible to manipulate DNS Answers from within those Scripts.