Almost all scanned images and photos require at least a bit of sharpening. What is sharpening?
Consider the image below of a dark grey circle on a light grey background...
This is a 'conceptual cross section' across the point marked with a red line:
A sharpen will identify all regions of high lightness contrast and accentuate the lightness values at the border:
This is what such a sharpen will look like (before left, after right).