We Know We Need It, But What Is SPF?

Beauty buzzwords are thrown around all the time; it can be hard to keep up and know what's worth exploring further. We're here to break down the industry's latest obsession by tackling the science, talking to skincare and makeup pros, and getting real about what works and what doesn’t.
We're told to wear SPF every day, and we know it prevents sun burn, skin damage, and the ageing process. But what exactly is SPF?