Though it's called "Gregory" Notation, this way of transcribing choreography is really a collaboration of Richard AND David. It works spectularly for describing weapon work, and really shines in large melee scenes. It can function for unarmed, but generally we go with text descriptions in those cases because of the nearly limitless possible variations of unarmed moves.

Basic Symbology

The symbols are placed on a series of parallel lines (like a musical stave), with one line for the actor's footwork below the line(s) for each of the actor's weapon. All the fighters on one side are placed together, opposed by all the fighters on the other side, reminiscent of the treble and bass clefs of musical notation.

The vertical lines ("measures") each represent a single beat of the fight, and in a large melee, everything that is simultaneous will line up vertically. This allows the fight to be "read" like music, and for the violence designer to know not only what happens, but when it happens relative to everything else.

Simple, no?