Source : Free On-Line Dictionary of Computing

dot file
     
         A {Unix} {application program}
        configuration file.  On {Unix}, files named with a leading dot
        are not normally shown in directory listings.  Many programs
        define one or more dot files in which startup or configuration
        information may be optionally recorded; a user can customise
        the program's behaviour by creating the appropriate file in
        the current or {home directory}.
     
        Dot files tend to proliferate - with every nontrivial
        application program defining at least one, a user's home
        directory can be filled with scores of dot files, without the
        user really being aware of it.  Common examples are .profile,
        .cshrc, .login, .emacs, .mailrc, .forward, .newsrc, .plan,
        .rhosts, .sig, .xsession.
     
        See also {profile}, {rc file}.
     
        [{Jargon File}]
     
        (1994-12-07)