For example: sales.yourdomain.com

A Sub Domain does not have to be registered! This makes Sub Domains an inexpensive option if you want another domain name. You can also point your sub-domain to your main website if you only want to have all your web pages under one website. You can have an unlimited number of Sub Domains. The only restriction is that you have the main domain name (ie yourdomain.com) hosted with us. And since you don't have to register your Sub Domain, you can use it right away without waiting for your domain registration or transfer to propagate throughout the net.

While many hosting companies charge you an additional $19.95/year for Unlimited Subdomains, Website Source Hosting offers it for free with all its hosting plans.