It can be anything! An apex, subdomain, or even a URL.
Domain Name: www.billing.darc.aiDomain Status: No Object Found>>> Last update of WHOIS database: 2024-09-22T17:28:34.826Z <<<
Domain Name: www.billing.darc.ai
Domain Status: No Object Found
>>> Last update of WHOIS database: 2024-09-22T17:28:34.826Z <<<