NAT64 is a mechanism to allow IPv6 hosts to communicate with IPv4 servers. The NAT64 server is the endpoint for at least one IPv4 address and an IPv6 network segment of 32-bits (for instance 64:ff9b::/96, see RFC 6052, RFC 6146). The IPv6 client embeds the IPv4 address it wishes to communicate with using these bits, and sends its packets to the resulting address. The NAT64 server then creates a NAT-mapping between the IPv6 and the IPv4 address, allowing them to communicate.
Read more about this topic: IPv6 Transition Mechanisms