Music Instrument Digital Interface (MIDI): Initially conceived as a way to connect synthesizers, MIDI was developed as an open standard that synth manufacturers could adopt to insure compatibility across all brands of gear. One device is connected to another with a cable. Device 1 can send little packets of data across the cable to device 2. These packets are called messages. The messages tell device 2 what device 1 wants it to do.
There are many types of MIDI controllers out there. Simple ones generally just change presets. The more elaborate controllers can do complicated combinations of commands and clocking. Most pedalboard owners will likely use MIDI for only two functions: controlling parameters (knobs, switches, etc.) and changing presets.
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