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

Results forkroot.strack.app

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-10-07T11:09:16.696	2020-10-07T10:09:16	2021-01-05T10:09:16	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-10-07T11:09:16.442	2020-10-07T10:09:16	2021-01-05T10:09:16	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-08-08T06:40:29.402	2020-08-08T05:40:29	2020-11-06T05:40:29	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-08-08T06:40:29.234	2020-08-08T05:40:29	2020-11-06T05:40:29	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-06-08T19:36:54.421	2020-06-08T18:36:54	2020-09-06T18:36:54	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-06-08T19:36:54.195	2020-06-08T18:36:54	2020-09-06T18:36:54	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-09T12:13:06.052	2020-04-09T11:13:05	2020-07-08T11:13:05	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-09T12:13:05.75	2020-04-09T11:13:05	2020-07-08T11:13:05	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-02-27T15:58:55.909	2020-02-27T14:58:55	2020-05-27T14:58:55	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-02-27T15:58:55.752	2020-02-27T14:58:55	2020-05-27T14:58:55	app.strack.app	kroot.strack.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3