Sunscreen is a lotion or cream that helps protect your skin from the harmful effects of the sun's rays. It works by absorbing or reflecting the sun's ultraviolet (UV) radiation, which can cause sunburn and increase the risk of skin cancer. Applying sunscreen is important, especially during sunny days or when spending time outdoors. To use sunscreen effectively, apply it generously to all exposed skin about 15-30 minutes before going outside. It's essential to choose a sunscreen with a high SPF (Sun Protection Factor) rating and to reapply it every two hours, or more often if swimming or sweating.