Now that your caching nameserver is working, it's time to tackle the other half of DNS: the resolver. As seen in Chapter 1, when a name lookup is required, a resolver performs the steps necessary to resolve the query. The details of the resolution will be taken care of by a nameserver, but your host OS needs a way to talk to the nameserver.
The OS resolver is not part of DNS, but it does use DNS for resolving hostnames. However, it also uses other sources. Chief among the other sources is the local /etc/hosts file and NIS (formerly known as YP). If the resolver configuration indicates that DNS should be used for hostname resolution, a local recursive DNS server is contacted and it performs the actual resolution described in