Burns are damage to the skin caused by heat or freezing. After a burn, there is a state of low blood flow to organs due to fluid loss. Burns also cause destruction of blood cells and increased capillary permeability, leading to swelling. Burns are classified by depth and severity. Depth is classified as first, second, or third degree. Severity depends on factors like size, depth, age, and medical history of the patient. The appearance, color, and symptoms indicate the depth and tissue damage of the burn.