secure.krm-tech.com is also a domain name. When Internet technical people say domain name, they don't mean just the domain krm-tech.com. Every name which is registered is a domain name, e.g. secure.krm-tech.com, mail.krm-tech.com,
www.krm-tech.com, and so forth.
The confusion of a
domain name with a
domain is understandable.
If you have a registrar for krm-tech.com, then it's likely they give you the facility to add more domain names to the domain, like mail.krm-tech.com,
www.krm-tech.com.