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

Results forapple.com.renderproxy.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2021-02-21T13:01:29.892	2021-02-21T12:01:29	2021-05-22T12:01:29	ww25.apple.com.renderproxy.com	ww25.apple.com.renderproxy.com	C=US, O=Let's Encrypt, CN=R3
2021-02-21T13:01:29.706	2021-02-21T12:01:29	2021-05-22T12:01:29	ww25.apple.com.renderproxy.com	ww25.apple.com.renderproxy.com	C=US, O=Let's Encrypt, CN=R3
2020-01-13T13:01:52.428	2020-01-13T12:01:52	2020-04-12T12:01:52	apple.com.renderproxy.com	apple.com.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-01-13T13:01:52.265	2020-01-13T12:01:52	2020-04-12T12:01:52	apple.com.renderproxy.com	apple.com.renderproxy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3