OAuth scopes are permission levels that define the extent of access granted to a third-party application when it interacts with an API. They allow users to control what data they share with applications, reducing risks and building user trust. OAuth scopes determine what parts of the API the app can access based on the user's consent, but the scope is granted in the context of the user's permissions. Implementing granular permissions via OAuth scopes involves defining scopes, requesting scopes during authorization, checking scopes in your API, and following best practices to ensure security and usability. By thoughtfully defining and enforcing scopes, you can offer more secure and flexible APIs, build user trust, and ensure that your applications follow best practices for data privacy.