AAAA is a domain record, that is basically the IPv6 address of the server where the domain is hosted. The IPv6 system was intended to replace the present IPv4 system where every IP address comprises of 4 groups of decimal numbers between 1 to 255 e.g. 18.104.22.168. In comparison, an IPv6 address has 8 sets of four hexadecimal digits - from 0 to 9 and from A to F. The cause of this transformation is the substantially smaller selection of unique IPs that the existing system supports as well as the rapid increase of gadgets that are connected to the Internet. A good example of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you want to direct a domain address to a web server which uses this type of an address, you'll have to set up an AAAA record for it, and not the widespread A record, which is an IPv4 address. The two records have the same exact function, but different notations are used, in order to distinguish the two forms of addresses.