This is an open source Android app and its entire source code is available on GitHub under the Apache 2.0 license.
This app does not connect to the internet in any way - in fact, as a zero-permission app, the Android operating system explicitly disallows internet access for this app in particular.
This app does allow the Android operating system to backup and restore its data automatically via the Auto Backup service, which involves app data being periodically backed up to your personal Google Drive account.
- For more information, see the Auto Backup service documentation and the Google Drive Terms of Service.
In addition, the app allows you to back up your notes onto your device's external storage, which could be accessible by other apps that hold the required permissions for accessing files from external storage.