The most well known group of effects, causing the addition of harmonics by cutting the amplitude of the signal.
Fuzz - the forerunner of all overdrives, cuts the signal very violently, giving a lot of harmonics and characteristic of the 60's "dirty" sound. It was the primary element of Jimmy Hendrix's sound, and today we are increasingly seeing them in the bassists,
Overdrive - Its task is to simulate a tube overdrive, it is not as predatory and sharp as a fuzz. In addition to using it as a separate overdrive, guitarists sometimes use it as a "preliminator" preamp. Allows to change the bandwidth and increase the overdrive. One of the most popular overdrive models is the Ibanez Tube Screamer.
Distortion - the strongest of the three, very aggressive and predatory, used in rock and metal music.
Boosters - they are not typical overdrives, their task is to raise the volume, frequency data or increase the overdrive.