An effects unit, effects processor, or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through audio signal processing.
A pedalboard allows a performer to create a ready-to-use chain of multiple pedals to achieve certain types of sounds. Signal chain order: tuner, compressor, octave generator, wah-wah pedal, overdrive, distortion, fuzz, EQ and tremolo.
An example of an effects chain. From the input [right] to the output [left]: Tuner [upper right] (tc electronic Polytune) ⇒ Wah pedal [lower right] (Morley Bad Horsie Wah) ⇒ Overdrives/distortion [lower row] (Rocktron Short Timer Delay → Danelectro CTO-1 Transparent Overdrive → Boss HM-2 → Boss MT-2) ⇒ Modulations/delay [upper row] (Digitech Hyper Phase → Danelectro CV-1 Vibe → Danelectro CT Tremolo → Digitech Hyper Delay)