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

Results fortransitable.com.transitable.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2025-02-10T13:17:45.311	2025-02-10T12:19:15	2025-05-11T12:19:14	transitable.com.transitable.com	transitable.com.transitable.com	C=US, O=Let's Encrypt, CN=R10
2025-02-10T13:17:45.094	2025-02-10T12:19:15	2025-05-11T12:19:14	transitable.com.transitable.com	transitable.com.transitable.com	C=US, O=Let's Encrypt, CN=R10
2020-03-06T09:08:18.026	2020-03-06T08:08:17	2020-06-04T08:08:17	transitable.com.transitable.com	transitable.com.transitable.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-03-06T09:08:17.771	2020-03-06T08:08:17	2020-06-04T08:08:17	transitable.com.transitable.com	transitable.com.transitable.com	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3