AAAA is a domain record, that is in essence the IPv6 address of the web server in which the domain name is hosted. The IPv6 system was introduced to replace the current IPv4 system where every single IP address consists of 4 groups of decimal numbers between 1 to 255 e.g. 18.104.22.168. In comparison, an IPv6 address features eight sets of four hexadecimal digits - from 0 to 9 and from A to F. The reason behind this change is the significantly smaller range of unique IPs which the existing system supports and the fast increase of products that are connected to the Internet. An example of an IPv6 address is 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you want to point a domain to a server which uses this kind of an address, you will need to set up an AAAA record for it, not the widely used A record, that is an IPv4 address. The two records deliver the exact same function, yet different notations are used, in order to distinguish the two types of addresses.