Discussing UV and sun protection, this video gives a short explanation of UPF ratings for clothing and how they work.
You will often see references to the ultraviolet protection factor, or UPF rating, in product descriptions for technical outdoor clothing including shirts, shorts, pants and hats. This specification is basically a sun protection rating, very similar to an SPF found on your sunscreen package. Typically, the higher the number of the UPF rating, the better protection level that clothing piece provides against ultraviolet rays from the sun.
UPFs are currently regulated by the EPA in the United States. Any company producing a garment that has a tag stating a UPF rating would have had to submit that garment for testing of that rating before it is made available for sale. This regulation provides some confidence to the consumer that the rating of any given garment is accurate.