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

Results for*.usem.mx

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2019-05-02T00:49:19.468	2019-04-27T00:00:00	2020-04-27T12:00:00	sni.cloudflaressl.com	*.usem.mx	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc ECC CA-2
2019-05-02T00:49:19.468	2019-04-27T00:00:00	2020-04-27T12:00:00	sni.cloudflaressl.com	*.usem.mx	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc ECC CA-2
2019-04-27T08:58:47.588	2019-04-27T00:00:00	2020-04-27T12:00:00	sni.cloudflaressl.com	*.usem.mx	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc ECC CA-2
2019-04-27T08:58:47.588	2019-04-27T00:00:00	2020-04-27T12:00:00	sni.cloudflaressl.com	*.usem.mx	C=US, ST=CA, L=San Francisco, O="CloudFlare, Inc.", CN=CloudFlare Inc ECC CA-2