CNAME both are types of DNS records, that can be applied to a domain name.
But they are mutually exclusive:
A resolves a domain name query to an IP address,
CNAME resolves it to an other domain name.
So if you are ”trying to point a subdomain to a different server“ it depends on you hosting situation if it's better to have DNS queries resolved directly to the new server's IP by setting the subdomain's
A record to the new IP or "redirect" the DNS lookup by setting
CNAME to point to a domain name of the new server (which gets DNS-resolved iteratively).
(I certainly have no crystal ball, but person asking the question may confuse a
CNAME record to be some kind of alias naming mechanism.)
- Actually, a domain name having a
CNAME attached must not have any other resource record associated.
- NB: In the case of HTTP requests to the mentioned subdomain, the
host: header will not change during a