Amazon S3 can be used for instances with root devices backed by local instance storage.
That way, developers have access to the same highly scalable, reliable, fast, inexpensive data storage infrastructure that Amazon uses to run its own global network of websites.
To execute systems in the Amazon EC2 environment, developers load Amazon Machine Images (AMIs) into Amazon S3 and then move them between Amazon S3 and Amazon EC2.
Amazon EC2 and Amazon S3 are two of the best-known web services that make up AWS.