you can say that subdomain is the extension of your domain. for example, if your domain is www.xyz.com, you can have a subdomain called hoovie.xyz.com
All the subdomains run separately as long as the root domain is still on.
you can add subdomain in DH panel easily. Go to “Domains” --> “Manage Domains”
Save [color=#CC0000]$97[/color] (max discount) on dreamhost by using promo code: [color=#CC0000]97CRAZY[/color].