AAAA is a domain name record, that is in essence the IPv6 address of the web server in which the domain is hosted. The IPv6 system was introduced to replace the current IPv4 system in which every IP address consists of four groups of decimal numbers ranging from 1 to 255 e.g. 5.168.208.143. However, an IPv6 address has 8 sets of 4 hexadecimal numbers - which range from 0 to 9 and from A to F. The reason behind this change is the substantially smaller selection of unique IPs which the existing system supports and also the quick increase of devices that are connected to the Internet. An illustration of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you wish to forward a domain name to a server that uses such an address, you'll have to set up an AAAA record for it, and not the commonly used A record, which is an IPv4 address. The 2 records have the same exact function, yet different notations are used, to separate the two forms of addresses.