Resource Owner Password Credentials (ROPC) is an OAuth 2.0 grant type that allows users to provide their username and password directly to a client application. This method is typically used in trusted applications where the user has a high level of trust in the application, such as mobile apps or first-party web applications. In ROPC, the client application exchanges the user's credentials for an access token, which can then be used to access protected resources. However, this approach is generally discouraged for public clients due to security risks, as it requires handling sensitive user credentials directly.