AAAA is a domain record, which is essentially the IPv6 address of the server where the domain is hosted. The IPv6 system was intended to replace the existing IPv4 system where every IP address is comprised of four sets of decimal digits between 1 to 255 e.g. 18.104.22.168. However, an IPv6 address has eight sets of four hexadecimal numbers - ranging from 0 to 9 and from A to F. The main reason for this change is the substantially smaller selection of unique IPs that the current system supports and the quick increase of units which are connected to the world wide web. An example of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you wish to direct a domain address to a machine that uses such an address, you will need to create an AAAA record for it, and not the widely used A record, which is an IPv4 address. The two records have the exact same function, yet different notations are used, to identify the two sorts of addresses.