Guitar pedals, also known as stompboxes, are external effects units that modify a guitar’s signal when activated. They come in various types, including distortion, overdrive, delay, reverb, modulation, EQ, compression, and synth effects, each shaping the tone in different ways. Pedals are typically placed on a pedalboard and powered by batteries or an external power supply. They can be connected in series for a custom signal chain, allowing guitarists to create unique sounds. Popular pedal brands include Boss, Electro-Harmonix, Strymon, MXR, and EarthQuaker Devices, offering effects for every genre, from blues and rock to ambient and experimental music.