What is Business Continuity Planning?

Legal Definition
Business continuity planning (or business continuity and resiliency planning) is the process of creating systems of prevention and recovery to deal with potential threats to a company.

Any event that could negatively impact operations is included in the plan, such as supply chain interruption, loss of or damage to critical infrastructure (major machinery or computing /network resource). As such, BCP is a subset of risk management.In the US, government entities refer to the process as continuity of operations planning (COOP).
-- Wikipedia
Legal Definition
Process of developing advance arrangements and procedures that enable an organization to respond to an event in such a manner that critical business functions continue with planned levels of interruption or essential change.