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

Results for*.holodeck.org

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2019-11-19T22:23:45.836	2019-11-17T00:00:00	2020-11-17T12:00:00	holodeck.org	*.holodeck.org	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G1
2019-11-19T22:23:45.836	2019-11-17T00:00:00	2020-11-17T12:00:00	holodeck.org	*.holodeck.org	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G1
2019-11-17T09:29:05.023	2019-11-17T00:00:00	2020-11-17T12:00:00	holodeck.org	*.holodeck.org	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G1
2019-11-17T09:29:05.023	2019-11-17T00:00:00	2020-11-17T12:00:00	holodeck.org	*.holodeck.org	C=US, O=DigiCert Inc, OU=www.digicert.com, CN=Encryption Everywhere DV TLS CA - G1