Don't let your lack of sunscreen smarts burn you this summer. A new survey in JAMA Dermatology shows that most people lack important sun protection knowledge, and don't understand much of what's written on lotion labels. According to Dr. Roopal Kundu, one of the study's authors and a dermatologist at Northwestern University Feinberg School of Medicine, a crucial aspect of picking the right sunscreen lies in the difference in UVB versus UVA protection. SPF (which stands for sun protection factor — something only 43 percent of people in the study knew) measures a sunscreen's ability to filter UVB rays, which are related to sunburn and skin cancer.