Imperfection and roughness are part of type history: in the predigital era, wood and metal letterforms wore down unevenly, and randomized differences were inevitable; truly consistent letterforms only became possible with digitized type. FF Beowolf brings uncertainty back to typography: it features a randomization feature in its code dictating that its forms change shape every time they are printed, so no letter will look the same twice. "A certain roughness or varying unevenness is quite pleasing to the eye," van Rossum has said. " . . . For reading, sameness is not necessary: we can read handwritten text, type superimposed on flickering TV images. The sameness of type seems an arbitrary thing that we can do away with in certain cases." In order to achieve this effect, they substituted the programming commands "lineto" and "curveto" in the PostScript code (PostScript is a computer program that describes what the outlines of letterforms are designed to look like) with their own command "freakto." "Freakto" causes a letter to be randomly generated with erratic outlines.
from Standard Deviations, 2011