It seems like there are 4 (or 5) different types of skins for Sims 4. It's like everyone 'magically' understands what these things mean. Even looking at download pages for sim modders who make skins they don't seem to explain what the difference is between a Skin Mask, Skin Overlay, and just a skin. i tried googling 'Sims 4, explain skin overlay, mask, normal' and i couldn't find answers, i tried different search terms too. I am very confused about the differences of skin types in sim 4. Please explain Skin Overlay, Skin Mask, Normal Skin, Etc