Adjustment layers are correction layers that adjust the color or tone of underlying layers without modifying the image layers themselves. You can add adjustment layers to test various color corrections or combinations of corrections. You can hide, delete, or edit adjustment layers.
An adjustment layer affects all layers below it. If an adjustment layer is in a layer group, it affects only the layers that are below it in the group. To apply an adjustment layer to a single layer without affecting the underlying layers, you can create a layer group with one layer and then add the adjustment layer above the layer in the group. Only the layer in the layer group is affected.
You can also add an adjustment layer by choosing Layers New Adjustment Layer.
You can also reset the values to the default by double-clicking the adjustment layer and clicking the Reset to Default button in the Properties dialog box.
You can also hide or display the adjustment layer overlay by clicking the Highlight mask area button on the Layers palette.
You can also open the Layer properties dialog box by choosing Layers Properties.