Folding paper by bending each fold in the opposite direction of the previous fold creating a pleated or accordion effect.
This works well for brochures that have a lot of graphics or photos with small blurbs of information that needs to be presented in an easy-access format with a small footprint, like those on a tourist rack or in a mailer.
See also: single fold, tri-fold, gate fold, zig-zag fold, barrel fold, french fold, map fold