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

Results forgitlab.blog.caption.cloud

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2023-07-22T15:30:54.808	2023-07-22T14:30:54	2023-10-20T14:30:53	gitlab.blog.caption.cloud	gitlab.blog.caption.cloud	C=US, O=Let's Encrypt, CN=R3
2023-07-22T15:30:54.698	2023-07-22T14:30:54	2023-10-20T14:30:53	gitlab.blog.caption.cloud	gitlab.blog.caption.cloud	C=US, O=Let's Encrypt, CN=R3
2023-04-22T08:47:17.045	2023-04-22T07:47:15	2023-07-21T07:47:14	gitlab.blog.caption.cloud	gitlab.blog.caption.cloud	C=US, O=Let's Encrypt, CN=R3
2023-04-22T08:47:16.207	2023-04-22T07:47:15	2023-07-21T07:47:14	gitlab.blog.caption.cloud	gitlab.blog.caption.cloud	C=US, O=Let's Encrypt, CN=R3
2022-10-23T22:54:14.42	2022-10-23T21:54:14	2023-01-21T21:54:13	gitlab.blog.caption.cloud	gitlab.blog.caption.cloud	C=US, O=Let's Encrypt, CN=R3
2022-10-23T22:54:14.342	2022-10-23T21:54:14	2023-01-21T21:54:13	gitlab.blog.caption.cloud	gitlab.blog.caption.cloud	C=US, O=Let's Encrypt, CN=R3