If you are masking a design prior to doing a separation, or masking a Texture Mapping scene, you can often end up with a lot of layers in the Layers Palette.
Converting layers into selections is a quick and easy way to keep your Layers Palette clean and organised.
Drag the layer from the Layers Palette to the Selections Palette and a selection will be created with the same name as the layer. If the layer is 8 bit, a tonal selection will be created.
Selections can be dragged back into the Layers Palette at any time, and will be converted back into a layer. This means, if you think the selection is not quite right, you can drag it to the Layers Palette, edit the layer, then drag it back to the Selections Palette.