Amazon Cognito Documentation

Amazon Cognito handles user authentication and authorization for your web and mobile apps. With user pools, you can easily and securely add sign-up and sign-in functionality to your apps. With identity pools (federated identities), your apps can get temporary credentials that grant users access to specific AWS resources, whether the users are anonymous or are signed in.

Amazon Cognito User Pools

Amazon Cognito Identity Pools (Federated Identities)

Amazon Cognito Sync

If you're new to Amazon Cognito Sync, use AWS AppSync instead. Both AWS AppSync and Amazon Cognito Sync synchronize application data across devices.