Good description of OAuth from one of the folks there at the beginning. I think the author doesn't do a great job of answering the question in the concrete, though. This sibling comment does a lot better[0].

I'm partial to this piece[1], which I helped write. It covers the various common modalities of OAuth/OIDC. (It's really hard to separate them, to be honest; they're often conflated.) Was discussed previously on HN[2].

0: https://news.ycombinator.com/item?id=47100073

1: https://fusionauth.io/articles/oauth/modern-guide-to-oauth

2: https://news.ycombinator.com/item?id=29752918