AAAA is a domain record, which is basically the IPv6 address of the web server in which the domain is hosted. The IPv6 system was introduced to replace the existing IPv4 system where every IP address consists of 4 sets of decimal numbers ranging from 1 to 255 e.g. 18.104.22.168. However, an IPv6 address includes eight groups of 4 hexadecimal digits - which range from 0 to 9 and from A to F. The reason behind this transformation is the substantially smaller amount of unique IPs the existing system supports and also the fast increase of products 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 to a server which uses this sort of an address, you will have to set up an AAAA record for it, not the widely used A record, which is an IPv4 address. Both records provide the very same function, but different notations are used, so as to distinguish the two types of addresses.