An AAAA record is an IP address in the recently introduced IPv6 format and it is made up of 8 sets of hexadecimal numbers, unlike the IPv4 IPs, which include 4 groups of numbers between 1 and 255. A good example of an IPv6 address is 3014:0d43:23a3:2354:1320:8f3b:2635:3254 and in this format the amount of IPs that could be created is many times bigger than the number of the IPv4 addresses. Every single domain name has its web hosting server IP as a record and in essence, this unique record informs the domain address where the site for it is located. Depending on the system the provider uses, the record will be called A (IPv4) or AAAA (IPv6). Changing this record will allow you to host your site with one provider and your emails with a different one, so if you decide to use such a redirection to point a domain name to a server that uses an IPv6 address, you'll have to set up an AAAA record for it.