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

Results forgroup2.tworksystem.org

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-05-26T07:32:58.887	2020-05-26T06:32:58	2020-08-24T06:32:58	tworksystem.org	*.tworksystem.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-05-26T07:32:58.703	2020-05-26T06:32:58	2020-08-24T06:32:58	tworksystem.org	*.tworksystem.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-09-22T03:15:58.016	2018-09-22T02:15:57	2018-12-21T02:15:57	group2.tworksystem.org	group2.tworksystem.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-09-22T03:15:57.767	2018-09-22T02:15:57	2018-12-21T02:15:57	group2.tworksystem.org	group2.tworksystem.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-07-24T03:32:23.157	2018-07-24T02:32:22	2018-10-22T02:32:22	group2.tworksystem.org	group2.tworksystem.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-07-24T03:32:22.532	2018-07-24T02:32:22	2018-10-22T02:32:22	group2.tworksystem.org	group2.tworksystem.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3