Step 1 : Introduction to the question "What does SPF on sunscreen products stand for?"
...Sunburn is a frequent cause of discomfort and injury during the summer months. The major cause of skin reddening and burn is the sun's ultraviolet B (UVB) rays. These rays can damage the skin's outer layers, the epidermis. This is where the most common forms of skin cancer originate. Fortunately, these are the least dangerous and tend to follow accumulated sun damage over the years. The SPF, or sun protection factor, of a sunscreen is a measure of how long you'll be protected by the product. The best protection, however, is to stay out of the sun during the peak hours (10 AM to 4 PM.) Source: ConsumerReports.org
