Establishing such a connection is optional. However, we strongly recommend performing this step. When you connect your game to Facebook (Android and iOS devices) or Apple ID (iOS devices only), your game account will be synchronized with the cloud.
If anything unexpected happens or you change the device, logging in to the same account on a respective platform will allow you to recover your progress. Note that you can play on multiple devices or transfer your progress to a new device with such a connection.
Important: Stay connected to ensure your progress is constantly backed up. Signing out will prevent synchronization until you sign in again.