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

Results forwww.blog.arrayconsultancy.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2018-09-08T13:31:18.75	2018-09-08T12:31:18	2018-12-07T12:31:18	blog.arrayconsultancy.com	www.blog.arrayconsultancy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-09-08T13:31:18.096	2018-09-08T12:31:18	2018-12-07T12:31:18	blog.arrayconsultancy.com	www.blog.arrayconsultancy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-07-08T21:35:00.919	2018-07-08T20:35:00	2018-10-06T20:35:00	blog.arrayconsultancy.com	www.blog.arrayconsultancy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-07-08T21:35:00.133	2018-07-08T20:35:00	2018-10-06T20:35:00	blog.arrayconsultancy.com	www.blog.arrayconsultancy.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3