According to the “Man Pages”:

gm                   (1)  - GraphicsMagick command-line utilities to create, edit, or convert images
[username@localhost ~]$ gm help
Version: GraphicsMagick 1.1.7 2005-10-12 Q8 http://www.GraphicsMagick.org/
Copyright: Copyright (C) 2002-2005 GraphicsMagick Group. Additional copyrights and licenses apply to this software, see http://www.GraphicsMagick.org/www/Copyright.html

Usage: gm help command [options ...]

Where options include: 
    animate - animate a sequence of images
  composite - composite images together
    conjure - execute a Magick Scripting Language (MSL) XML script
    convert - convert an image or sequence of images
    display - display an image on a workstation running X
       help - obtain usage message for named command
   identify - describe an image or image sequence
     import - capture an application or X server screen
    mogrify - transform an image or sequence of images
    montage - create a composite image (in a grid) from separate images
    version - obtain release version

so there you have it for a brief and to the point cheat sheet for Graphics Magick! Enjoy…