Subdomain (subdomain) is a part of the domain name, but stands at a lower level in the hierarchy of domain names. Any domain name can be inherited from an unlimited number of subdomains that are derived from it. The name of each sub-domain is placed before the domain name and is separated by a dot (".")

Example:
Domain Name: your_name.net

subdomains:
office.your_name.net
info.your_name.net
backoffice.your_name.net etc.