From the source:

> The Obverse-End Wizards know how to make the Smoke colorful, and make it display letters in a myriad styles, and allow the Onlooker to manipulate the Smoke themselves.

> The Reverse-End Wizards have magics to move knowledge along the many threads of the Web, bringing it to the Smoke for the Onlooker to See, or from the Onlooker to some distant node of the Web where it will be processed into something of use

> The Obverse- and Reverse-End Wizards commonly work together; sometimes they are even the same person, and we call them the Full-Stack Wizards (stack is a corruption of tzahua, meaning to spin or weave, referring to the Great Web).