So you would use this on a initialized repo that has no remote repo?
From the title, you would use this if you're trying to pull new file versions from another repo when the directory you're on doesn't have a remote repo because you use git init on it?
Yes, and usually the remote will be a repo that's hosted online. The online repo will get updated on Github/Bitbucket/whatever via a pull request and having it set as the remote on your local repo will allow you to git pull from it.
Let me know if this helps!