Final answer:
Critical systems are the essential systems for a nation or organization, while mission essential functions are the necessary tasks to accomplish the mission of an organization. They are prioritized and protected to ensure the resilience of a nation's infrastructure.
Step-by-step explanation:
Critical systems are the systems that are essential for the functioning and survival of a nation or organization. These systems include things like communication networks, power grids, transportation systems, and water supply systems. Mission essential functions are the tasks and activities that are necessary to accomplish the mission of an organization or agency. For example, in the case of a government agency, mission essential functions might include things like law enforcement, emergency response, and national defense.
In the context of civil defense and emergency preparedness, critical systems and mission essential functions are prioritized and protected to ensure the resilience of a nation's infrastructure. This involves implementing measures such as anti-terrorism legislation and developing strategies to mitigate and respond to various threats and hazards.