Some Layer Mask Tricks
You can do a few more things with layer masks to enhance your Photoshop prowess:Ctrl+click/z +click the layer mask thumbnail in the Layers palette to create a layer mask-shaped selection.
Click the layer mask thumbnail in the Layers palette to select it, and then choose Image>Adjustments>Invert to reverse the effects of the layer mask. Visible areas become hidden and hidden areas revealed.