Always On AGs are SQL Server’s high availability and disaster recovery (DR) technology.

Always On Availability Groups (AGs) provide database-level high availability (HA) with automatic failover for user databases.

It replaces the older Database Mirroring technology(deprecated from 2016) Up to eight secondary replicas support by AGs.

In the case of any failure on the primary database, all of the databases within an AG will failover together and the Secondary Server becomes active.

Active Secondary can be used for backups, read-only workload to reduce some of the load away from the primary