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

Results fortest.admin.smartlinkgo.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2021-09-22T20:08:19.548	2021-09-22T19:08:19	2021-12-21T19:08:18	test.admin.smartlinkgo.com	test.admin.smartlinkgo.com	C=US, O=Let's Encrypt, CN=R3
2021-09-22T20:08:19.263	2021-09-22T19:08:19	2021-12-21T19:08:18	test.admin.smartlinkgo.com	test.admin.smartlinkgo.com	C=US, O=Let's Encrypt, CN=R3
2021-01-29T14:07:26.644	2021-01-29T13:07:26	2021-04-29T13:07:26	test.admin.smartlinkgo.com	test.admin.smartlinkgo.com	C=US, O=Let's Encrypt, CN=R3
2021-01-29T14:07:26.396	2021-01-29T13:07:26	2021-04-29T13:07:26	test.admin.smartlinkgo.com	test.admin.smartlinkgo.com	C=US, O=Let's Encrypt, CN=R3