You can smooth the hard edges of a selection by anti-aliasing or feathering. Anti-aliasing smoothes the jagged edges of a selection by softening the color transition between edge pixels and background pixels. Because only the edge pixels change, no detail is lost. Anti-aliasing is useful when cutting, copying, and pasting selections to create composite images.
You can select anti-aliasing with the Lasso, Polygonal Lasso, Magnetic Lasso, Elliptical Marquee, and Magic Wand tools. To anti-alias, you must select the Anti-Alias option before making the selection; you cannot add anti-aliasing to an existing selection.