Frostbite refers to skin and tissue damage caused by freezing temperatures below -0.55°C. It is most common in people spending long periods outdoors, the very young/old, and those with circulation problems or taking medications that constrict blood vessels. When exposed to cold, the body prioritizes core warmth by constricting blood vessels in the extremities, causing them to freeze. Frostbite symptoms range from numbness to blistering and blackened skin depending on severity. Immediate first aid includes slowly rewarming the affected area and seeking medical help to assess damage and prevent complications like infection or tissue death.