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

Results forbeta.prek.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2019-12-04T07:19:20.662	2019-12-04T06:19:20	2020-03-03T06:19:20	www.lingosong.com	beta.prek.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-12-04T07:19:20.451	2019-12-04T06:19:20	2020-03-03T06:19:20	www.lingosong.com	beta.prek.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-10-03T19:44:40.092	2019-10-03T18:44:39	2020-01-01T18:44:39	www.rxhub.eu	beta.prek.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-10-03T19:44:39.742	2019-10-03T18:44:39	2020-01-01T18:44:39	www.rxhub.eu	beta.prek.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-10-03T17:37:29.632	2019-10-03T16:37:28	2020-01-01T16:37:28	beta.prek.com	beta.prek.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-10-03T17:37:28.577	2019-10-03T16:37:28	2020-01-01T16:37:28	beta.prek.com	beta.prek.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3