Masks
Changing mask mode
Mask mode determines what parts of a layer are visible when a mask is applied. You can choose between regular mode, which shows only content under the mask, or inverse mode, which shows everything except the area under the mask.
Select a layer that has a mask applied, then in the Properties panel, use the MASK toggle to switch between Regular and Inverse modes. Regular mode shows only content under the mask, while Inverse mode shows everything except the mask area.
Next, learn to adjust rounding for smooth mask edges or apply a mask to a layer.
Try changing mask mode yourself, below.