I used to use the example of Dropbox’s chooser API to illustrate this: https://www.dropbox.com/developers/chooser

If you use this API (via a simple widget library) then the user simply picks a file in their dropbox and the app gets access to that one file. Vs OAuth where you grant the app broad access to the whole dropbox (or maybe some sub-folder).

What you're describing is the difference between Fine Grained Authorization (FGA) and traditional Role-based Access Control (RBAC). This article covers the difference: https://www.osohq.com/learn/what-is-fine-grained-authorizati... (disclaimer: I used to work there but continue to be a fan of their documentation).