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

Results forwww.chat.trung.dev

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2021-06-02T07:26:39.842	2021-06-02T06:26:39	2021-08-31T06:26:39	www.review.trung.dev	www.chat.trung.dev	C=US, O=Let's Encrypt, CN=R3
2021-06-02T07:26:39.645	2021-06-02T06:26:39	2021-08-31T06:26:39	www.review.trung.dev	www.chat.trung.dev	C=US, O=Let's Encrypt, CN=R3
2021-04-02T08:06:47.597	2021-04-02T07:06:47	2021-07-01T07:06:47	www.senior.trung.dev	www.chat.trung.dev	C=US, O=Let's Encrypt, CN=R3
2021-04-02T08:06:47.393	2021-04-02T07:06:47	2021-07-01T07:06:47	www.senior.trung.dev	www.chat.trung.dev	C=US, O=Let's Encrypt, CN=R3
2021-01-31T08:04:57.134	2021-01-31T07:04:56	2021-05-01T07:04:56	www.hr.trung.dev	www.chat.trung.dev	C=US, O=Let's Encrypt, CN=R3
2021-01-31T08:04:56.977	2021-01-31T07:04:56	2021-05-01T07:04:56	www.hr.trung.dev	www.chat.trung.dev	C=US, O=Let's Encrypt, CN=R3
2020-12-01T07:23:20.43	2020-12-01T06:23:20	2021-03-01T06:23:20	www.chat.trung.dev	www.chat.trung.dev	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-12-01T07:23:20.151	2020-12-01T06:23:20	2021-03-01T06:23:20	www.chat.trung.dev	www.chat.trung.dev	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3