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 specific file from an Amazon Simple Storage Service (Amazon S3) bucket, your credentials must allow that access. If your credentials aren't authorized to download the file, AWS denies your request.
In some cases, you can make calls to AWS without security credentials, such as downloading a file that is publicly shared in an Amazon S3 bucket.