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

Results for*.challengebase.lifull.net

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-02-12T01:45:19.27	2020-02-12T00:00:00	2021-03-12T12:00:00	*.challengebase.lifull.net	*.challengebase.lifull.net	C=US, O=Amazon, OU=Server CA 1B, CN=Amazon
2020-02-12T01:45:19.27	2020-02-12T00:00:00	2021-03-12T12:00:00	*.challengebase.lifull.net	*.challengebase.lifull.net	C=US, O=Amazon, OU=Server CA 1B, CN=Amazon
2020-02-12T01:36:58.185	2020-02-12T00:00:00	2021-03-12T12:00:00	challengebase.lifull.net	*.challengebase.lifull.net	C=US, O=Amazon, OU=Server CA 1B, CN=Amazon
2020-02-12T01:36:58.185	2020-02-12T00:00:00	2021-03-12T12:00:00	challengebase.lifull.net	*.challengebase.lifull.net	C=US, O=Amazon, OU=Server CA 1B, CN=Amazon