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

Results fornode.kissandcode.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2018-10-09T19:21:07.794	2018-10-09T18:21:07	2019-01-07T18:21:07	node.kissandcode.com	node.kissandcode.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-09T19:21:07.65	2018-10-09T18:21:07	2019-01-07T18:21:07	node.kissandcode.com	node.kissandcode.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-04T17:57:20.368	2018-10-04T16:57:20	2019-01-02T16:57:20	node.kissandcode.com	node.kissandcode.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-04T17:57:20.134	2018-10-04T16:57:20	2019-01-02T16:57:20	node.kissandcode.com	node.kissandcode.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-04T16:40:52.702	2018-10-04T15:40:51	2019-01-02T15:40:51	node.kissandcode.com	node.kissandcode.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-04T16:40:51.987	2018-10-04T15:40:51	2019-01-02T15:40:51	node.kissandcode.com	node.kissandcode.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3