The Fluent Design System helps you create modern, bold UI that incorporates light, depth, motion, material, and scale. Acrylic is a Fluent Design System component that adds physical texture (material) and depth to your app.
Acrylic is a type of Brush that creates a partially transparent texture. You can apply acrylic to app surfaces to add depth and help establish a visual hierarchy.
Learn more at: https://docs.microsoft.com/en-us/windows/uwp/style/acrylic