Source : Free On-Line Dictionary of Computing

diff
     
        /dif/ 1. A change listing, especially giving differences
        between (and additions to) different versions of a piece of
        source code or documentation (the term is often used in the
        plural "diffs").  "Send me your diffs for the Jargon File!"
     
        Compare {vdiff}.
     
        2. Specifically, such a listing produced by the diff {Unix}
        command, especially when used as input to the {patch} utility
        (which actually performs the modifications).  This is a common
        method of distributing patches and source updates.
     
        3. To compare (whether or not by use of automated tools on
        machine-readable files).
     
        See also {vdiff}, {mod}.
     
        [{Jargon File}]
     
        (1995-02-10)