If you wish to point a domain address that you have to another domain name or subdomain, one way to do that would be to use a CNAME record. By setting up such a record, the domain address being redirected loses all its records (A, MX, etc) and instead, it takes the A record of the domain name it is directed to. That way, if you are using a web design service by some company that gives you a subdomain, you can use an actual domain name and not only will it be directed to the site which you have set up, but it'll also appear in the web browser address bar at all times. Alternative possible uses of a CNAME record are to forward all of the traffic from various subdomains to their main domain name, or to use the webmail service of your webhosting company by using webmail.your-doman.com, for example. The latter will work only by creating a CNAME record for a subdomain simply because such a record created for the main domain renders it impossible to use email addresses.