There are two categories of sunscreen ingredients, physical and chemical.
Physical sunscreen ingredients like zinc oxide and titanium dioxide protect the skin by reflecting the light rays.
Chemical sunscreen ingredients like avebenzone and oxybenzone absorb the light rays to protect the skin from damage.
Physical sunscreens do a better job of protecting the skin from sun damage and chemical sunscreens allow products to have a lighter feel and be water resistant. Many popular brands use a combination of physical and chemical sunscreen ingredients to produce the most user friendly product.
As an esthetician who works with a lot of clients suffering from hyper-pigmentation or melasma (often called “sun spots”), I am a fan of physical sunscreens. There is less opportunity for allergic reactions and they are safer for acne prone/sensitive skin as well.