AAAA is a domain address record, that's basically the IPv6 address of the web server in which the domain name is hosted. The IPv6 system was introduced to replace the present IPv4 system where each IP address is made up of 4 groups of decimal digits which range from 1 to 255 e.g. 18.104.22.168. In comparison, an IPv6 address includes 8 sets of 4 hexadecimal numbers - ranging from 0 to 9 and from A to F. The reason for this transformation is the tremendously smaller range of unique IPs which the present system supports as well as the rapid increase of units which are connected to the Internet. An illustration of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you'd like to forward a domain to a machine that uses this kind 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. The 2 records have the exact same function, but different notations are used, to differentiate the two types of addresses.