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

Results forapi.dev.hbot.io

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2018-05-04T12:42:24.179	2018-05-04T11:42:23	2018-08-02T11:42:23	api.dev.hbot.io	api.dev.hbot.io	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-05-04T12:42:24.01	2018-05-04T11:42:23	2018-08-02T11:42:23	api.dev.hbot.io	api.dev.hbot.io	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-03-05T09:11:17.213	2018-03-05T08:11:17	2018-06-03T08:11:17	api.dev.hbot.io	api.dev.hbot.io	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-01-04T10:08:13.593	2018-01-04T09:08:13	2018-04-04T09:08:13	api.dev.hbot.io	api.dev.hbot.io	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-01-04T09:19:48.639	2018-01-04T08:19:48	2018-04-04T08:19:48	api.dev.hbot.io	api.dev.hbot.io	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2017-10-27T16:37:40.564	2017-10-27T15:37:40	2018-01-25T15:37:40	api.dev.hbot.io	api.dev.hbot.io	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2017-10-17T11:23:45.899	2017-10-17T10:23:45	2018-01-15T10:23:45	api.dev.hbot.io	api.dev.hbot.io	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3