Sign in with your Apple ID using app-specific passwords
App-specific passwords allow you to securely use your Apple ID to sign in to apps made by developers other than Apple.
Our App ask you to sign in with your Apple ID, so that the app can sync iCloud account calendars events that you store in iCloud. To help make sure that your Apple ID password can’t be stored or collected by the app, you need to use an Apple ID password with that app.
You use this app-specific password when the app asks you to sign in with your Apple ID.
To generate and use app-specific passwords, your Apple ID must be protected with two-factor authentication.