AAAA is a domain record, that is essentially the IPv6 address of the server in which the domain name is hosted. The IPv6 system was intended to replace the current IPv4 system in which each IP address consists of four sets of decimal digits which range from 1 to 255 e.g. 188.8.131.52. In contrast, an IPv6 address includes 8 sets of 4 hexadecimal numbers - from 0 to 9 and from A to F. The cause of this transformation is the significantly smaller number of unique IPs which the present system supports and also the fast increase of units that are connected to the world wide web. A good example of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you'd like to point a domain name to a machine that uses such an address, you will need 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, but different notations are used, to distinguish the two sorts of addresses.