A 'CNAME' record or canonical name records make one domain alias of another. The aliased domain gets all the subdomain and DNS records of the original.
You should use a 'CNAME' record whenever you want to assossiate a new domain to an already existing 'A' record that is you can make www.subdomain.tld to subdomain.tld which should already have been assigned an ip with an 'A' record.This allows you to have many subdomains as you wish without have been assigned to an ip with an 'A' record.
eg:
stuff.everybox.com. IN CNAME www.everybox.com.
where www.everybox.com is an 'A' record listing an ip address and stuff.example.com points to www.example.com
