Defrag is like your momma cleaning your bedroom. You know where everything belongs and should go but you just throw it whereever. Momma comes along and puts it away right. Nothing is moved. Your dresser, bed and toybox are int the same place they are just cleaned up. Compacting means you have a lot of socks and undies so momma just pushes them down so the drawer will shut. Moving files means the shoes under the bed go in the closet and dirty underwear goes in the wash. If momma finds something that ain't right or broken that is referred to Dad/Scandisk.