A CNAME record is a canonical name record. CNAME records are used to alias one name to another hostname. For example, in the DNS for greatmail.com, the following CNAME record creates an alias zap.greatmail.com that refers to the hostname www.foo.com:
zap IN CNAME www.foo.com.
This CNAME record would redirect ‘zap.greatmail.com’ to ‘www.foo.com’.