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

Results forwebdisk.myabo.cf

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2019-01-11T17:02:52.202	2019-01-11T16:02:50	2019-04-11T16:02:50	measplayer.com	webdisk.myabo.cf	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-01-11T17:02:50.921	2019-01-11T16:02:50	2019-04-11T16:02:50	measplayer.com	webdisk.myabo.cf	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-11-11T17:04:55.958	2018-11-11T16:04:55	2019-02-09T16:04:55	myabo.cf	webdisk.myabo.cf	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-11-11T17:04:55.512	2018-11-11T16:04:55	2019-02-09T16:04:55	myabo.cf	webdisk.myabo.cf	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-09-11T16:00:53.642	2018-09-11T15:00:53	2018-12-10T15:00:53	player.tk	webdisk.myabo.cf	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-09-11T16:00:53.407	2018-09-11T15:00:53	2018-12-10T15:00:53	player.tk	webdisk.myabo.cf	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-07-11T21:33:48.361	2018-07-11T20:33:47	2018-10-09T20:33:47	myabo.cf	webdisk.myabo.cf	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-07-11T21:33:47.231	2018-07-11T20:33:47	2018-10-09T20:33:47	myabo.cf	webdisk.myabo.cf	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3