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

Results forcodenail.com.renderproxy.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-01-20T21:58:27.941	2020-01-20T20:58:27	2020-04-19T20:58:27	www.codenail.com.renderproxy.com	www.codenail.com.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-01-20T21:58:27.738	2020-01-20T20:58:27	2020-04-19T20:58:27	www.codenail.com.renderproxy.com	www.codenail.com.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-01-20T21:10:09.562	2020-01-20T20:10:09	2020-04-19T20:10:09	codenail.com.renderproxy.com	codenail.com.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-01-20T21:10:09.297	2020-01-20T20:10:09	2020-04-19T20:10:09	codenail.com.renderproxy.com	codenail.com.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3