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

Results forsubscriptions.yeezysoftware.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-05-17T10:32:04.314	2020-05-17T09:32:03	2020-08-15T09:32:03	subscriptions.acutescan.com	subscriptions.yeezysoftware.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-05-17T10:32:04.083	2020-05-17T09:32:03	2020-08-15T09:32:03	subscriptions.acutescan.com	subscriptions.yeezysoftware.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-03-17T18:01:19.581	2020-03-17T17:01:19	2020-06-15T17:01:19	subscriptions.yeezysoftware.com	subscriptions.yeezysoftware.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-03-17T18:01:19.33	2020-03-17T17:01:19	2020-06-15T17:01:19	subscriptions.yeezysoftware.com	subscriptions.yeezysoftware.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3