The short version: if you want to use S3 from outside of AWS - for example in a cron script that backs up a VPS to S3 - you need an access key and a secret key. This tool helps you create credentials that are very tightly scoped, for example that can only read and write to one specific S3 bucket, not your entire AWS account.
I released a new version yesterday which added the ability to create credentials that can only access files within a prefix (or folder) within an S3 bucket: https://simonwillison.net/2022/Jan/18/weeknotes/
The short version: if you want to use S3 from outside of AWS - for example in a cron script that backs up a VPS to S3 - you need an access key and a secret key. This tool helps you create credentials that are very tightly scoped, for example that can only read and write to one specific S3 bucket, not your entire AWS account.
I released a new version yesterday which added the ability to create credentials that can only access files within a prefix (or folder) within an S3 bucket: https://simonwillison.net/2022/Jan/18/weeknotes/