AAAA is a domain record, that's in essence the IPv6 address of the server in which the domain is hosted. The IPv6 system was intended to replace the existing IPv4 system where each and every IP consists of 4 groups of decimal numbers between 1 to 255 e.g. 126.96.36.199. In contrast, an IPv6 address includes 8 groups of 4 hexadecimal numbers - from 0 to 9 and from A to F. The reason behind this modification is the substantially smaller number of unique IPs which the current system supports as well as the fast increase of products that are connected to the Internet. A good example of an IPv6 address would be 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you'd like to direct a domain to a web server that uses this kind of an address, you have to set up an AAAA record for it, not the commonly used A record, that is an IPv4 address. The 2 records deliver the same exact function, yet different notations are used, so as to separate the two types of addresses.