AAAA is a domain record, which is basically the IPv6 address of the web server where the domain name is hosted. The IPv6 system was intended to replace the current IPv4 system in which every single IP address comprises of 4 groups of decimal numbers ranging from 1 to 255 e.g. 18.104.22.168. In contrast, an IPv6 address includes 8 groups of 4 hexadecimal numbers - from 0 to 9 and from A to F. The cause of this modification is the significantly smaller amount of unique IPs the existing system supports as well as the rapid increase of gadgets which are connected to the Internet. An example of an IPv6 address is 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you need to direct a domain to a machine which uses this sort of an address, you need to set up an AAAA record for it, not the commonly used A record, that is an IPv4 address. Both records provide the exact same function, but different notations are used, so as to separate the two forms of addresses.