AAAA is a domain address record, which is essentially the IPv6 address of the server where the domain name is hosted. The IPv6 system was intended to replace the existing IPv4 system in which each IP comprises of four sets of decimal digits ranging from 1 to 255 e.g. 18.104.22.168. On the other hand, an IPv6 address has eight sets of four hexadecimal digits - ranging from 0 to 9 and from A to F. The main reason for this change is the considerably smaller range of unique IPs that the current system supports and also the fast increase of gadgets that 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 direct a domain to a machine which uses such an address, you will have to set up an AAAA record for it, not the widespread A record, that is an IPv4 address. The two records have the exact same function, but different notations are used, so as to differentiate the two forms of addresses.