AAAA is a domain record, that's essentially the IPv6 address of the web server where the domain name is hosted. The IPv6 system was designed to replace the existing IPv4 system where each and every IP address comprises of 4 groups of decimal digits which range from 1 to 255 e.g. 126.96.36.199. On the other hand, an IPv6 address has 8 sets of 4 hexadecimal digits - which range from 0 to 9 and from A to F. The reason behind this modification is the significantly smaller number of unique IPs which the existing system supports and the fast increase of gadgets which are connected to the world wide web. An example of an IPv6 address is 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you wish to forward a domain name to a machine that uses this type of an address, you will need to set up an AAAA record for it, not the widespread A record, that is an IPv4 address. Both records provide the same exact function, yet different notations are used, to separate the two forms of addresses.