It can be anything! An apex, subdomain, or even a URL.

Results forstaging.hostmaster.stonegod.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-12-16T07:38:19.635	2020-12-16T06:38:19	2021-03-16T06:38:19	staging.hostmaster.stonegod.com	staging.hostmaster.stonegod.com	C=US, O=Let's Encrypt, CN=R3
2020-12-16T07:38:19.486	2020-12-16T06:38:19	2021-03-16T06:38:19	staging.hostmaster.stonegod.com	staging.hostmaster.stonegod.com	C=US, O=Let's Encrypt, CN=R3
2020-10-02T22:22:34.527	2020-10-02T21:22:34	2020-12-31T21:22:34	staging.hostmaster.stonegod.com	staging.hostmaster.stonegod.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-10-02T22:22:34.291	2020-10-02T21:22:34	2020-12-31T21:22:34	staging.hostmaster.stonegod.com	staging.hostmaster.stonegod.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3