I was wondering how GitHub templates differentiates from forks and why should I use them instead of forking a repository?
As far as I understood, you can't pull updates from templates the same way you can pull them from forks. You are unable to push changes to the forked repository as well.
Templates are intended to use a repository as-is, and to use it as a boilerplate to build for example a website. It's not meant to be up-to-date with the main repository.
Edit: Also you can't fork your own repositories on GitHub; you can however use your own templates.