Cleaned means that someone has used a chemical or mechanical method to alter the coin's surfaces - silver/copper polish, "dip", jewelry cleaner, emery/cloth/scotch-brite pads, fine steel wool, those are just a few of the methods.
Cleaning a coin in most, but not all, cases substantially reduces its value.
A details coin is named because something about the coin prevents it from getting a full grade. Cleaning, damage, holes, scratches/graffiti, bends, gouges, corrosion, and many other things can affect the surfaces of a coin - when this happens a third-party grading company will assign a DETAILS grade, qualifying the nature of the injury to the coin. Again, in most, but not all, cases, a details grade reduces the value of a coin.
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