The Feather EdgesΓÇ¥ option of the selection tools, but you may feather them again with this command.
command feathers the edges of the selection. This creates a smooth transition between the selection and its surroundings. You normally feather selection borders with the ΓÇ£Enter the width of the selection border feathering. The default units are pixels, but you can also choose other units with the drop-down menu.