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

Results formagento.mkt.renderproxy.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-02-09T12:33:49.855	2020-02-09T11:33:49	2020-05-09T11:33:49	www.magento.mkt.renderproxy.com	www.magento.mkt.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-02-09T12:33:49.508	2020-02-09T11:33:49	2020-05-09T11:33:49	www.magento.mkt.renderproxy.com	www.magento.mkt.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-02-09T12:20:45.166	2020-02-09T11:20:44	2020-05-09T11:20:44	magento.mkt.renderproxy.com	magento.mkt.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-02-09T12:20:44.933	2020-02-09T11:20:44	2020-05-09T11:20:44	magento.mkt.renderproxy.com	magento.mkt.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3