How are documents stored and what's the difference between amazonaws.com and internal/document/preview urls?

Can anyone explain the technical details of document storage? We are starting to share some PDF links stored in a project that is shared systemwide out to large groups via MS Teams and emails (these PDFs are things like process docs) and have discovered that the s3.amazonaws.com link is more or less temporary - it throws a page not found error sometime after the initial send of the link. Not sure why. However, the “yourdomain.my.workfront.com/internal/document/preview" link that redirects to the amazonaws link does seem to work for sharing.