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

Results fordevzilla.disroot.org

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2019-06-15T23:56:55.216	2019-06-15T22:56:54	2019-09-13T22:56:54	devzilla.disroot.org	devzilla.disroot.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-06-15T23:56:54.116	2019-06-15T22:56:54	2019-09-13T22:56:54	devzilla.disroot.org	devzilla.disroot.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-04-03T06:45:07.559	2019-04-03T05:45:06	2019-07-02T05:45:06	devzilla.disroot.org	devzilla.disroot.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-04-03T06:45:06.223	2019-04-03T05:45:06	2019-07-02T05:45:06	devzilla.disroot.org	devzilla.disroot.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-01-02T20:39:54.901	2019-01-02T19:39:54	2019-04-02T19:39:54	devzilla.disroot.org	devzilla.disroot.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-01-02T20:39:54.328	2019-01-02T19:39:54	2019-04-02T19:39:54	devzilla.disroot.org	devzilla.disroot.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-10T21:41:28.787	2018-10-10T20:41:28	2019-01-08T20:41:28	devzilla.disroot.org	devzilla.disroot.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-10-10T21:41:28.326	2018-10-10T20:41:28	2019-01-08T20:41:28	devzilla.disroot.org	devzilla.disroot.org	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3