The 5 W's of sunscreen are: 1. Who: Everyone, regardless of age or skin type, should use sunscreen. 2. What: Use a broad-spectrum sunscreen with at least SPF 30. 3. When: Apply sunscreen 15 minutes before sun exposure and reapply every two hours or after swimming or sweating. 4. Where: Apply to all exposed skin, including face, neck, ears, and the tops of feet. 5. Why: To protect against harmful UV rays, prevent sunburn, reduce the risk of skin cancer, and prevent premature aging.