Sunblock, also known as sunscreen, is a lotion or cream applied to the skin to protect it from the harmful effects of the sun's ultraviolet (UV) rays. It works by either absorbing or reflecting these rays, helping to prevent sunburn and reduce the risk of skin cancer. Sunblock is available in various forms, including lotions, sprays, and sticks, and is often labeled with a Sun Protection Factor (SPF) rating that indicates its effectiveness. To be effective, sunblock should be applied generously and evenly to all exposed skin at least 15 minutes before sun exposure. It is important to reapply it every two hours, or more often if swimming or sweating. Using sunblock is a key part of sun safety, along with wearing protective clothing and seeking shade, especially during peak sun hours.