AWS security credentials - AWS General Reference

AWS security credentials

When you interact with AWS, you specify your AWS security credentials to verify who you are and whether you have permission to access the resources that you are requesting. AWS uses the security credentials to authenticate and authorize your requests.

For example, if you want to download a protected file from an Amazon Simple Storage Service (Amazon S3) bucket, your credentials must allow that access. If your credentials don't show you are authorized to download the file, AWS denies your request. However, your AWS security credentials aren't required for you to download a file in an Amazon S3 bucket that is publicly shared.