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

Results forprojects.ironhack.com.mx

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2019-01-30T15:44:11.806	2019-01-30T14:44:10	2019-04-30T14:44:10	smogy.eu	projects.ironhack.com.mx	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2019-01-30T15:44:10.918	2019-01-30T14:44:10	2019-04-30T14:44:10	smogy.eu	projects.ironhack.com.mx	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-11-30T05:44:01.811	2018-11-30T04:44:01	2019-02-28T04:44:01	www.darentradadpvat.com.br	projects.ironhack.com.mx	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-11-30T05:44:01.29	2018-11-30T04:44:01	2019-02-28T04:44:01	www.darentradadpvat.com.br	projects.ironhack.com.mx	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-11-29T23:08:55.086	2018-11-29T22:08:54	2019-02-27T22:08:54	projects.ironhack.com.mx	projects.ironhack.com.mx	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2018-11-29T23:08:54.069	2018-11-29T22:08:54	2019-02-27T22:08:54	projects.ironhack.com.mx	projects.ironhack.com.mx	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3