Masks let you shape how parts of your design look by using layers like shapes, text, or pictures. Think of a mask as a stencil placed over your design elements. Whatever part of the design is under the mask shows through, while the rest is hidden.

These masks are easy to find in the Layers panel because they're marked with an icon of interlaced shapes. The layers being shaped by the mask have an upward arrow.

Here's a simple way to understand it: masks act like a layer sitting just under the ones they affect. They change everything directly above them until they hit another mask or the edge of their group. This makes it easy to mix and match different parts of your design creatively.