Final answer:
The AWS S3 feature for automatic management of objects is called S3 Lifecycle management, which allows for changes in storage classes and auto-deletion.
Step-by-step explanation:
The AWS S3 feature that allows for automatic changing of objects' storage classes and deletion of objects is called S3 Lifecycle management. This feature is designed to help users save costs by automating the migration of objects to the most cost-effective storage class and purging objects that are no longer needed. With a lifecycle policy, you can define rules for transitioning objects to different storage classes such as S3 Standard-Infrequent Access (IA) or S3 Glacier for archival, or rules for automatic deletion after a certain period or at a specific date. This ensures that data is stored in the most cost-effective manner and helps maintain data that is frequently accessed in more readily accessible storage classes without manual intervention.