Its many time seen, so many people often confused or thought High Availability and Disaster Recovery (DR) are the same thing. A high-availability solution does not mean that you are prepared for a disaster. High availability covers hardware or system-related failures, whereas disaster recovery can be used in the event of a catastrophic failure due to environmental factors. Although some of the high-availability options may help us when designing our DR strategy, they are not the be-all and end-all solution.
The goal of high availability is to provide an uninterrupted user experience with zero data loss. According to Microsoft’s SQL Server Books Online, “A high-availability solution masks the effects of a hardware or software failure and maintains the availability of applications so that the perceived downtime for users is minimized”.
Disaster recovery is generally a part of a larger process known as Business Continuity Planning (BCP), which plans for any IT or non IT eventuality. A server disaster recovery plan helps in undertaking proper preventive, detective and corrective measures to mitigate any server related disaster. Here is the very good book “The Shortcut Guide To Untangling the Differences Between High Availability and Disaster Recovery” by Richard Siddaway for more details. As per my understanding below explanation is the best and quickest way to remember this is:

High Availability is @ LAN and Disaster Recovery is @ WAN

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