Source : Free On-Line Dictionary of Computing

tool bar
     
         A common {graphical user interface}
        component, consisting of a permanently visible row of button
        {icons} which, when clicked with the {mouse}, cause the
        program to perform some action such as printing the current
        document or changing the {mode} of operation.
     
        The tool bar buttons often duplicate functions accessible via
        {menus} but are easier to use since they are permanently
        visible.  A typical use would be in a {paint} program where
        the tool bar allows the users to select one of the various
        painting "tools" - brush, pencil, bucket etc.
     
        Some {application programs} under some {operating systems} may
        allow the user to customise the functions accessible via
        toolbars, in others the choice is fixed by the programmer.
     
        (2000-02-09)