These are like A records, but they allow you to point domains or subdomaints to IPv6 addresses. (A records point to IPv4 addresses.) When people say AAAA records out loud, they usually pronounce them as quad-A records.
AAAA records are less common than A records, but they are growing in popularity as the use of IPv6 grows, too. You can use AAAA records in a similar way to A records, including setting up at-records and wildcard configurations.
The value you enter for AAAA records must be an IPv6 address.