The Auto Sharpen command increases clarity or focus without the risk of oversharpening an image.
The Sharpen tool focuses soft edges in a photo to increase clarity or focus. Oversharpening a photo gives it a grainy look. You can avoid oversharpening by setting a lower Strength value in the options bar. It’s best to make the sharpening subtle and increase it as necessary by dragging over the area several times, building up the sharpness each time.
The Adjust Sharpness dialog box has sharpening controls not available with the Sharpen tool or with Auto Sharpen. You can set the sharpening algorithm or control the amount of sharpening that occurs in shadow and highlight areas.