Which AWS services and features are provided to all customers at no charge?

Explanations:

Amazon Aurora is a managed database service that is not free; it incurs costs based on the resources used, including storage, I/O operations, and instances.

Amazon VPC (Virtual Private Cloud) allows users to create isolated networks within the AWS cloud at no charge. Users only pay for the resources used within the VPC.

Amazon SageMaker is a machine learning service that is not free; charges are based on the resources and services used, such as instances and storage.

AWS Identity and Access Management (IAM) is provided at no cost to all AWS customers, enabling them to manage user access and permissions without additional charges.

Amazon Polly is a text-to-speech service that charges based on the number of characters processed, so it is not available at no charge.