Critical infrastructure refers to assets and systems that are essential to society's functioning. This includes sectors like water, energy, food, health, transport, communications, finance, government, and emergency services. Critical infrastructure is vulnerable to natural disasters, technological failures, terrorism, and other hazards. Protecting critical infrastructure involves assessing risks, prioritizing vulnerabilities, implementing protection programs, and continuously improving resilience through measures like redundant systems and emergency planning. The level of protection and regulation can vary along a continuum from market forces to government ownership.