This tutorial covers implementing two-factor authentication for an Android app using Nexmo's Verify API endpoints, specifically focusing on sending verification requests and checking verification codes via a proxy server setup. The app uses Retrofit for networking and Moshi for JSON serialization/deserialization. It stores the phone number and request ID in SharedPreferences to cancel or check the status of any verification request. The network requests are similar to those made earlier to start the verification process, with error handling for responses. The app also includes a "Cancel" button to handle cancellation of the verification request.