Custom Domains lets you associate any of your web domains with a Site. A Custom Domain is usually a combination of a domain name and a subdomain. For example, cdn.mydomain.com for your content or www.mydomain.com for your website. The Custom Domain is then translated into an IP address via the Domain Name System (DNS).
You can serve content off any domain or sub-domain you choose, as long as you properly point each domain to the CNAME/ANAME Target via your DNS manager.
However, Custom Domains are optional because you can deliver content right from your Site’s Highwinds Domain. What's my Highwinds Domain, you ask? It's the same as your CNAME Target.
Custom Domains allows you to specifiy the unique domains end-users use to access your content, and the CDN uses to identify your content.
This is the additive list used for identifying each of your Custom Domains.