I found this gem while looking for some learning material.
https://www.thesitewizard.com/domain/website-without-domain-name.shtml
It's not about that article specifically.
But the whole page is literally filled with usefull information.
@ravenclaw before I clicked on that I thought it was about running a website with just an IP address
W3.org also really cool.
But it's like a common secret.