AAAA is a domain record, that's essentially the IPv6 address of the server where the domain name is hosted. The IPv6 system was designed to replace the current IPv4 system where each and every IP address comprises of 4 groups of decimal digits which range from 1 to 255 e.g. 220.127.116.11. In contrast, an IPv6 address has 8 groups of four hexadecimal digits - ranging from 0 to 9 and from A to F. The cause of this change is the tremendously smaller number of unique IPs the current system supports and also the rapid increase of gadgets which are connected to the Internet. An example of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you need to forward a domain address to a web server that uses this sort of an address, you have to set up an AAAA record for it, not the widely used A record, which is an IPv4 address. The two records provide the very same function, yet different notations are used, so as to distinguish the two types of addresses.