When you apply an effect to an ordinary layer, the effect applies only to that layer and no others. However, an effect can exist independently if you create an adjustment layer for it. Any effects applied to an adjustment layer affect all layers below it in the layer stacking order. An adjustment layer at the bottom of the layer stacking order has no visible result.

Because effects on adjustment layers apply to all layers beneath them, they are useful for applying effects to many layers at once. In all other respects, an adjustment layer behaves exactly like other layers; for example, you can use keyframes or expressions with any adjustment layer property.

Use masks on an adjustment layer to apply an effect to only parts of the underlying layers. You can animate masks to follow moving subjects in the underlying layers.