.Use a raster selection to create a mask that shows or hides the selection. Use this mask as a starting point for creating artistic effects.
To create masks from selections on vector layers, use the Selection, Freehand Selection, and Magic Wand tools. You cannot use the Object Selection tool.
To create a mask from a selection:
Use the Selection, Freehand Selection, or Magic Wand tool to make a selection on a raster or vector layer in the image.
Do either of the following:
To mask the selection, choose Layers > New Mask Layer > Hide Selection.
To mask everything except the selection, choose Layers > New Mask Layer > Show Selection.
The mask layer and the selected layer are added to a new layer group. The mask layer applies to the selected layer only. To apply it to all underlying layers, drag it from the layer group to the main level.
For information on editing the mask, see Editing Masks.
To view the mask on the image, on the Layer palette click the Mask Overlay toggle .