AAAA is a domain record, that's in essence 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 IP is comprised of four sets of decimal numbers ranging from 1 to 255 e.g. 126.96.36.199. On the other hand, an IPv6 address features 8 groups of four hexadecimal numbers - from 0 to 9 and from A to F. The reason behind this modification is the considerably smaller amount of unique IPs the present system supports and also the fast increase of units which are connected to the Internet. A good example of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you wish to forward a domain to a server which uses this kind of an address, you'll have to set up an AAAA record for it, not the widely used A record, that is an IPv4 address. Both records have the very same function, yet different notations are used, in order to differentiate the two forms of addresses.