The iStomp is basically a compact multi effects pedal loaded with one effect at a time. You can choose from almost 50 software ePedals (Overdrive, Distortion, Vibrato, Delay, Phaser, Flanger, Tremolo, Clean Boost, Reverb, Compressor, Chorus, Octaver, ...) which can be transferred via cable from an iOS device to the iStomp. Most of the ePedals are free. Some are actually accurate emulations of real pedals (e. g. the DOD Overdrive Preamp/250 or the DOD FX13 Gonkulator). The iStomp can be controlled by adjusting four knobs. The functions of those knobs depend on the effect. There are two input jacks and two output jacks as some ePedals offer stereo functionality.