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

Results forcn-eastsun.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-09-07T19:52:10.886	2020-09-07T18:52:10	2020-12-06T18:52:10	cn-eastsun.com	cn-eastsun.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-09-07T19:52:10.171	2020-09-07T18:52:10	2020-12-06T18:52:10	cn-eastsun.com	cn-eastsun.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-09-04T14:59:54.717	2019-09-04T13:59:54	2019-12-03T13:59:54	cn-eastsun.com	cn-eastsun.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-09-04T14:59:54.06	2019-09-04T13:59:54	2019-12-03T13:59:54	cn-eastsun.com	cn-eastsun.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-09-04T14:58:56.314	2019-09-04T13:58:55	2019-12-03T13:58:55	www.xgmcable.com	cn-eastsun.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-09-04T14:58:55.492	2019-09-04T13:58:55	2019-12-03T13:58:55	www.xgmcable.com	cn-eastsun.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3