Amazon DynamoDB is a fully managed non-relational (NoSQL) database service that provides fast and predictable performance with seamless scalability. As a managed service, it handles tasks such as hardware provisioning, setup and configuration, replication, software patching, and scaling, making it an appropriate choice. In contrast, Amazon RDS is a managed relational database service; Amazon EC2 instances must be managed by the user, although AWS helps with provisioning; and Amazon S3 is an object storage service, not a database service.