It can be anything! An apex, subdomain, or even a URL.
Domain Name: app.upper.aiDomain Status: No Object Found>>> Last update of WHOIS database: 2024-09-21T10:51:06.228Z <<<
Domain Name: app.upper.ai
Domain Status: No Object Found
>>> Last update of WHOIS database: 2024-09-21T10:51:06.228Z <<<