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

Results for*.ctrbook.top

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-08-17T01:40:44.504	2020-08-17T00:00:00	2021-08-17T12:00:00	sni.cloudflaressl.com	*.ctrbook.top	C=US, O="Cloudflare, Inc.", CN=Cloudflare Inc ECC CA-3
2020-08-17T01:40:44.504	2020-08-17T00:00:00	2021-08-17T12:00:00	sni.cloudflaressl.com	*.ctrbook.top	C=US, O="Cloudflare, Inc.", CN=Cloudflare Inc ECC CA-3
2020-04-02T05:54:19.768	2020-04-02T00:00:00	2020-10-09T12:00:00	sni.cloudflaressl.com	*.ctrbook.top	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc ECC CA-2
2020-04-02T05:54:19.768	2020-04-02T00:00:00	2020-10-09T12:00:00	sni.cloudflaressl.com	*.ctrbook.top	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc ECC CA-2