DNS uses A and AAAA (called quad A) records for resolving a domain name to an IP address. To determine a host name based on the IP address, DNS uses the reverse lookup.
The A record can store a 32-bit address and is used to resolve IPv4 addresses. The AAAA record can store a 128-bit address and is used to resolve IPv6 addresses.
IPv4 reverse DNS lookups use the in-addr.arpa domain. An IPv4 address is represented in the in-addr.arpa domain by a sequence of bytes, represented as decimal numbers, in reverse order. The numbers are separated by dots and end with the suffix .in-addr.arpa.
IPv6 reverse DNS lookups use the ip6.arpa domain. An IPv6 address is represented as a name in the ip6.arpa domain by a sequence of nibbles, represented as hexadecimal digits, in reverse order. These nibbles are separated by dots and end with the suffix .ip6.arpa.