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

Results for*.af.edu

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-01-29T03:10:17.744	2009-01-15T18:13:34	2012-01-16T18:13:34	leap.af.edu	*.af.edu	C=US, O=U.S. Government, OU=DoD, OU=PKI, CN=DOD CA-18
2020-01-29T03:10:17.744	2009-01-15T18:13:34	2012-01-16T18:13:34	leap.af.edu	*.af.edu	C=US, O=U.S. Government, OU=DoD, OU=PKI, CN=DOD CA-18
2020-01-29T03:10:17.445	2009-01-21T19:21:20	2012-01-22T19:21:20	dra.af.edu	*.af.edu	C=US, O=U.S. Government, OU=DoD, OU=PKI, CN=DOD CA-18
2020-01-29T03:10:17.445	2009-01-21T19:21:20	2012-01-22T19:21:20	dra.af.edu	*.af.edu	C=US, O=U.S. Government, OU=DoD, OU=PKI, CN=DOD CA-18