Distortion, Overdrive, Fuzz

Overdrive, Distortion, and Fuzz all work similarly by boosting your signal and overlaying it to simulate, to various degrees, of overpowering an old tube amp with overlaying harmonics.  The various types allow you to have sound from a "warm" slightly overdriven sound to a hard, heavy metal crunch or a fuzz as associated with the Stones riff in Satisfaction.