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

Results forsitemap.crowdreference.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2021-06-02T13:49:05.113	2021-06-02T12:49:04	2021-08-31T12:49:04	sitemap.crowdreference.com	sitemap.crowdreference.com	C=US, O=Let's Encrypt, CN=R3
2021-06-02T13:49:04.895	2021-06-02T12:49:04	2021-08-31T12:49:04	sitemap.crowdreference.com	sitemap.crowdreference.com	C=US, O=Let's Encrypt, CN=R3
2021-03-09T03:46:58.377	2021-03-09T02:46:58	2021-06-07T02:46:58	sitemap.crowdreference.com	sitemap.crowdreference.com	C=US, O=Let's Encrypt, CN=R3
2021-03-09T03:46:58.166	2021-03-09T02:46:58	2021-06-07T02:46:58	sitemap.crowdreference.com	sitemap.crowdreference.com	C=US, O=Let's Encrypt, CN=R3
2020-12-14T04:38:17.465	2020-12-14T03:38:16	2021-03-14T03:38:16	sitemap.crowdreference.com	sitemap.crowdreference.com	C=US, O=Let's Encrypt, CN=R3
2020-12-14T04:38:16.872	2020-12-14T03:38:16	2021-03-14T03:38:16	sitemap.crowdreference.com	sitemap.crowdreference.com	C=US, O=Let's Encrypt, CN=R3