A useful enhancement should make the intended subject easier to see while preserving the evidence and character of the source image.
For a portrait, the improvement may appear as cleaner shadows, more legible eyes, and less distracting noise. For a scanned family image, the useful change may be restored contrast and clearer separation between hair, clothing, and background. For a product photo, the result should make edges and surfaces easier to inspect without changing the product's actual shape or colour. Save the original file first, compare the versions at full size, and keep the enhanced copy separate from the camera original. That simple habit makes it easier to reverse an overprocessed edit.
Enhance a photo