UVA vs UVB
Sunlight is made up of both visible and invisible electromagnetic rays. The visible is what we think of as sunshine, as opposed to the invisible, which occurs on the other two ends of the color spectrum. There are invisible wavelengths beyond red, known as infrared, on one end and others beyond violet, known as ultraviolet, or UV light on the other. It is the UV rays that are important to the health of our skin.
UVs come from the sun in three different wavelengths – UVA, UVB and UBC. UVA and UVB matter the most to humans. Simply put, UVA causes skin to age and wrinkle; UVB causes sunburns in the short run and skin cancers in the long run.