Amazon Cognito is a service that provides authentication, authorization, and user management for web and mobile applications. It allows for user sign-up, sign-in, access control, account recovery, and integration with social identity providers. Cognito User Pools provides built-in user directory and authentication services, while Cognito Identity Pools enables the generation of temporary AWS credentials for application access. Sample use cases include business to consumer apps, business to employee apps, and IoT applications.