AAAA is a domain record, which is basically the IPv6 address of the server in which the domain is hosted. The IPv6 system was designed to replace the current IPv4 system in which each Internet protocol address consists of 4 sets of decimal digits ranging from 1 to 255 e.g. 18.104.22.168. In comparison, an IPv6 address includes 8 sets of four hexadecimal numbers - which range from 0 to 9 and from A to F. The reason behind this transformation is the tremendously smaller amount of unique IPs which the current system supports and also the rapid increase of units which are connected to the world wide web. An example of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you wish to point a domain to a web server which uses such an address, you have to set up an AAAA record for it, and not the widespread A record, which is an IPv4 address. The two records have the very same function, yet different notations are used, to differentiate the two forms of addresses.