Quick answer: A records map a hostname to an IPv4 address, AAAA records map it to IPv6, and CNAME records create an alias to another hostname.
A and AAAA records
A is the classic IPv4 address record. AAAA is the corresponding record for IPv6. A dual-stack website can publish both.
CNAME records
A CNAME points a hostname at another hostname rather than directly storing an IP address. This is useful when a service provider wants customers to use a stable name while the underlying addresses change.
Check a domain
Use DNS Lookup to inspect the records currently returned for a domain. For a fuller reference, read our DNS record types guide.
Want to see this in practice? Check your own connection's IP, location and ISP.
Check my IP address