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

Results forwww.fileserver.best4software.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2021-04-24T10:06:08.199	2021-04-24T09:06:07	2021-07-23T09:06:07	fileserver.best4software.com	*.fileserver.best4software.com	C=US, O=Let's Encrypt, CN=R3
2021-04-24T10:06:08.02	2021-04-24T09:06:07	2021-07-23T09:06:07	fileserver.best4software.com	*.fileserver.best4software.com	C=US, O=Let's Encrypt, CN=R3
2021-02-17T15:17:36.657	2021-02-17T14:17:36	2021-05-18T14:17:36	fileserver.best4software.com	*.fileserver.best4software.com	C=US, O=Let's Encrypt, CN=R3
2021-02-17T15:17:36.498	2021-02-17T14:17:36	2021-05-18T14:17:36	fileserver.best4software.com	*.fileserver.best4software.com	C=US, O=Let's Encrypt, CN=R3
2020-12-20T11:04:47.116	2020-12-20T10:04:46	2021-03-20T10:04:46	fileserver.best4software.com	*.fileserver.best4software.com	C=US, O=Let's Encrypt, CN=R3
2020-12-20T11:04:46.91	2020-12-20T10:04:46	2021-03-20T10:04:46	fileserver.best4software.com	*.fileserver.best4software.com	C=US, O=Let's Encrypt, CN=R3