What is the difference between backup, replication, and high availability?

Backup creates recoverable copies of data for restoration after loss or corruption. Replication maintains additional copies that follow changes from a source. High availability is the broader capability to keep a service operating through failures, often using redundancy and automated failover.

Replication is not a substitute for backup because accidental deletion or corruption can be replicated. High availability is not disaster recovery because a highly available primary environment can still suffer a site-wide disaster.