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

Results foritem.dev.bitesize.guru

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-06-17T05:21:11.348	2020-06-17T04:21:11	2020-09-15T04:21:11	locall.hitevent.com	item.dev.bitesize.guru	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-06-17T05:21:11.13	2020-06-17T04:21:11	2020-09-15T04:21:11	locall.hitevent.com	item.dev.bitesize.guru	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-19T18:17:06.053	2020-04-19T17:17:05	2020-07-18T17:17:05	www.uestc.icu	item.dev.bitesize.guru	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-19T18:17:05.838	2020-04-19T17:17:05	2020-07-18T17:17:05	www.uestc.icu	item.dev.bitesize.guru	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-19T15:56:25.93	2020-04-19T14:56:25	2020-07-18T14:56:25	item.dev.bitesize.guru	item.dev.bitesize.guru	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-04-19T15:56:25.696	2020-04-19T14:56:25	2020-07-18T14:56:25	item.dev.bitesize.guru	item.dev.bitesize.guru	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3