This is a quite capable analog distortion module with multiple modes.
You can use this as a saturator, overdrive, or as a fuzz module depending on how you use it and define those terms.
Saturation
We use opamps and diodes to add harmonics to the waveform. Using the controls OD1 and OD2, you can add distortion to the upper half or lower half of the waveform.
You can increase the control GAIN to increase the overall distortion.
Overdrive
Turning both OD1 and OD2 to the right will turn this module into an overdrive.
Fuzz
Output sockets labeled as DIRTY go through another diode-based drive circuit to add more harmonics. You can use the output socket labeled as CLEN to bypass this circuit.