Every step, a random walker chooses a random direction (of its 8 grid neighbors) to move to. The pixels are colored based on how often a particular square was touched by the walker (e.g., a position that was only touched twice would be less colored than one that the walker reached 50 times, with darker colors indicating it was touched more).
Walker Turn Chance is the probability that the walker will change direction each step, so lower settings will make the walker tend to take more straight paths more than wander around.
Pixel Coloring Intensity affects how much the weight of a tile is multiplied to make patterns stand out more (so that tiles touched more than once stand out more from tiles never touched).
Selecting "Black or White" for Pixel Coloring Mode will make every cell be either white (if it was touched less than half the average) or black (if it was touched more than half the average).
Turning on Inverse Pixel Coloring will make every pixel be drawn as the inverse of its actual color (so that more-visited cells will be drawn ligher, instead of darker).