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

Results forcodedemo.work.a.bdydns.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2021-10-26T12:37:23.297	2021-10-26T11:37:22	2022-01-24T11:37:21	apply.codedemo.work.a.bdydns.com	apply.codedemo.work.a.bdydns.com	C=US, O=Let's Encrypt, CN=R3
2021-10-26T12:37:23.035	2021-10-26T11:37:22	2022-01-24T11:37:21	apply.codedemo.work.a.bdydns.com	apply.codedemo.work.a.bdydns.com	C=US, O=Let's Encrypt, CN=R3
2021-07-23T17:19:12.059	2021-07-23T16:19:11	2021-10-21T16:19:09	apply.codedemo.work.a.bdydns.com	apply.codedemo.work.a.bdydns.com	C=US, O=Let's Encrypt, CN=R3
2021-07-23T17:19:11.6	2021-07-23T16:19:11	2021-10-21T16:19:09	apply.codedemo.work.a.bdydns.com	apply.codedemo.work.a.bdydns.com	C=US, O=Let's Encrypt, CN=R3
2021-03-18T05:28:48.435	2021-03-18T04:28:48	2021-06-16T04:28:48	open.aapp.work.a.bdydns.com	open.codedemo.work.a.bdydns.com	C=US, O=Let's Encrypt, CN=R3
2021-03-18T05:28:48.297	2021-03-18T04:28:48	2021-06-16T04:28:48	open.aapp.work.a.bdydns.com	open.codedemo.work.a.bdydns.com	C=US, O=Let's Encrypt, CN=R3