That you can publish a repo to github pages in settings and the URL is:
https://username.github.io/repo
Name a repo: username.github.io
And Publish to GitHub Pages
Becomes our base URL, and that repo is published to it
Add a custom domain name to our username.github.io repo...
Does that turn the base URL username.github.io customdomain.com
All other published repos to customdomain.com/repo
I did not mention, is configuring your Domain Name Provider to point to GitHub, which is as easy as changing one thing,
Change to: 192.30.252.153
@bwreid
By Tommy Gaessler
Custom Domain Names and Hosting with GitHub Pages
Developer Advocate at Zoom