How can SQL server AlwaysOn AG can be used as a DR feature?
AlwaysOn supports multiple replica databases, so you can have one replica as your HA database, and another replica as your DR database. AlwaysOn is great in that one technology potentially provides your HA and your DR.

The HA database would typically be in the same datacentre, and be set to synchronous commit with automatic failover. The DR database would typically be in another datacentre, but because of the latency it would typically be asynchronous as first choice. This means that data-loss is possible. You could experiment to see whether the DR replica, set as synchronous, performs well enough for your application.

Please remember that if you use AlwaysOn as your DR technology, you still need to take database backups like normal - and get them shipped off the server.