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

Results for403995g45.secure0029.hubspot.net

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2018-03-01T15:54:42.541	2018-03-01T00:00:00	2019-03-01T12:00:00	403995g45.secure0029.hubspot.net	403995g45.secure0029.hubspot.net	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc ECC CA-2
2018-03-01T15:54:41.665	2018-03-01T00:00:00	2019-03-01T12:00:00	403995g45.secure0029.hubspot.net	403995g45.secure0029.hubspot.net	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc RSA CA-1
2018-03-01T15:54:39.782	2018-03-01T00:00:00	2018-08-10T12:00:00	403995g45.secure0029.hubspot.net	403995g45.secure0029.hubspot.net	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc Compatibility CA-3