Survivalism is a social movement of individuals or groups (called survivalists or preppers) who proactively prepare for emergencies, including natural disasters, as well as disruptions to social, political, or economic order. Preparations may anticipate short-term scenarios or long-term, on scales ranging from personal adversity, to local disruption of services, to international or global catastrophe. Survivalism may be limited to preparing for a personal emergency, such as job loss or being stranded in the wild or under adverse weather conditions. The emphasis is on self-reliance, stockpiling supplies, and gaining survival knowledge and skills. Survivalists often acquire emergency medical and self-defense training, stockpile food and water, prepare to become self-sufficient, and build structures such as survival retreats or underground shelters that may help them survive a catastrophe.