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

Results forauth.antemo.de

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2019-09-25T14:15:37.459	2019-09-25T13:15:36	2019-12-24T13:15:36	*.antemo.de	*.antemo.de	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-09-25T14:15:36.408	2019-09-25T13:15:36	2019-12-24T13:15:36	*.antemo.de	*.antemo.de	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-06-30T16:08:15.03	2019-06-30T15:08:14	2019-09-28T15:08:14	*.antemo.de	*.antemo.de	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-06-30T16:08:14.46	2019-06-30T15:08:14	2019-09-28T15:08:14	*.antemo.de	*.antemo.de	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-04-01T13:24:20.316	2019-04-01T12:24:19	2019-06-30T12:24:19	antemo.de	*.antemo.de	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-04-01T13:24:19.621	2019-04-01T12:24:19	2019-06-30T12:24:19	antemo.de	*.antemo.de	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-01-18T16:27:58.63	2019-01-18T15:27:57	2019-04-18T15:27:57	auth.antemo.de	auth.antemo.de	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-01-18T16:27:57.057	2019-01-18T15:27:57	2019-04-18T15:27:57	auth.antemo.de	auth.antemo.de	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3