What is the difference between backup and retention / email archival?

What is the difference between backup and retention / email archival?

Backup is for recovery from hardware failure or recent data corruption or loss while Retention / Email Archive is for legal compliance and long term data retention.

There are various laws like Sarbanes Oxley (SOX), HIPAA, FDIC, etc. that apply to various industries mandating data archival for legal compliance. Organizations that fall under these industry categories would be required to retain emails (incoming, outgoing and internal).​