AAAA is a domain name record, that's essentially the IPv6 address of the web server where the domain is hosted. The IPv6 system was intended to replace the existing IPv4 system in which every single IP is made up of 4 sets of decimal numbers ranging from 1 to 255 e.g. 18.104.22.168. However, an IPv6 address features 8 groups of 4 hexadecimal digits - which range from 0 to 9 and from A to F. The main reason for this modification is the tremendously smaller range of unique IPs the current system supports as well as the rapid increase of gadgets which are connected to the Internet. A good example of an IPv6 address is 2101:1f34:32e2:2415:1365:4f2b:2553:1345. If you'd like to point a domain to a machine which uses such an address, you will have to create an AAAA record for it, not the widespread A record, which is an IPv4 address. Both records have the very same function, yet different notations are used, in order to differentiate the two types of addresses.