A Reverse Zone is a zone file that contains only PTR records and a SOA record. This type of zone file allows the mapping of an IP Address to a hostname/domain name.

Ninety-percent of DNS behavior concerns the translating or mapping of hostnames into numbered (IP) addresses, otherwise considered a Forward Zone. When this happens, a (human readable) hostname or domain name is translated to the (computer readable) IP Address.

The remaining 10% are Reverse Zones, where the mapping is reversed and occurs from IP Address to the hostname.