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

Results forapi.plan.achook.dev

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2021-04-14T08:21:05.24	2021-04-14T07:21:04	2021-07-13T07:21:04	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Let's Encrypt, CN=R3
2021-04-14T08:21:04.928	2021-04-14T07:21:04	2021-07-13T07:21:04	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Let's Encrypt, CN=R3
2021-02-14T03:43:39.899	2021-02-14T02:43:39	2021-05-15T02:43:39	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Let's Encrypt, CN=R3
2021-02-14T03:43:39.335	2021-02-14T02:43:39	2021-05-15T02:43:39	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Let's Encrypt, CN=R3
2020-12-16T22:59:52.893	2020-12-16T21:59:52	2021-03-16T21:59:52	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Google Trust Services, CN=GTS CA 1D2
2020-10-18T19:08:32.413	2020-10-18T18:08:31	2021-01-16T18:08:31	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Google Trust Services, CN=GTS CA 1D2
2020-08-20T15:17:11.687	2020-08-20T14:17:10	2020-11-18T14:17:10	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Google Trust Services, CN=GTS CA 1D2
2020-06-19T16:13:50.902	2020-06-19T15:13:49	2020-09-17T15:13:49	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Google Trust Services, CN=GTS CA 1D2
2020-04-18T17:10:38.613	2020-04-18T16:10:38	2020-07-17T16:10:38	api.plan.achook.dev	api.plan.achook.dev	C=US, O=Google Trust Services, CN=GTS CA 1D2