He a very smol boi. He is a tiny USB MIDI controller with 2 knobs, to buttons and one mini jack input for DIY sensors and shit.
To make a DIY sensor connect a potentiometer or construct some other voltage divider. The tip of the minijack is +5V, the sleeve is GND and the ring is where the voltage is measured by the midimalism and turned sent to your pooter as MIDI data. DONT SHORT +5V AND GND, midimalism might probably maybe die.