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

Results forwww.dev.eth1.me

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2022-01-04T15:20:34.338	2022-01-04T14:20:33	2022-04-04T14:20:32	www.dev.eth1.me	www.dev.eth1.me	C=US, O=Let's Encrypt, CN=R3
2022-01-04T15:20:33.857	2022-01-04T14:20:33	2022-04-04T14:20:32	www.dev.eth1.me	www.dev.eth1.me	C=US, O=Let's Encrypt, CN=R3
2018-12-21T20:41:30.233	2018-12-21T19:41:29	2019-03-21T19:41:29	dev.eth1.me	www.dev.eth1.me	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-12-21T20:41:29.773	2018-12-21T19:41:29	2019-03-21T19:41:29	dev.eth1.me	www.dev.eth1.me	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-22T12:42:29.923	2018-10-22T11:42:29	2019-01-20T11:42:29	dev.eth1.me	www.dev.eth1.me	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-22T12:42:29.247	2018-10-22T11:42:29	2019-01-20T11:42:29	dev.eth1.me	www.dev.eth1.me	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3