CNAME” records, short for “Canonical Name”, create an alias from a domain name to another. You could create an alias from “yahoo.mydomain.com” to “www.yahoo.com”, and every reference to “yahoo.mydomain.com” would go to the other location, regardless how yahoo changed their IP addresses! Be careful, however; CNAMEs won’t work everywhere. If you create an MX record, and the name used for the mail server was defined using a CNAME, you might lose e-mail!