AAAA is a domain name record, which is in essence the IPv6 address of the server in which the domain is hosted. The IPv6 system was intended to replace the current IPv4 system in which each and every IP is comprised of 4 sets of decimal numbers which range from 1 to 255 e.g. 184.108.40.206. In contrast, an IPv6 address has eight groups of 4 hexadecimal digits - ranging from 0 to 9 and from A to F. The reason behind this transformation is the considerably smaller selection of unique IPs that the current system supports and the fast 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 to a web server which uses such an address, you'll have to set up an AAAA record for it, and not the widespread A record, which is an IPv4 address. Both records deliver the exact same function, yet different notations are used, so as to differentiate the two sorts of addresses.