The acronym MIDI stands for “Musical Instrument Digital Interface.” In the simplest explanation, MIDI is a language (technically speaking, it’s a protocol) that allows digitally-controlled musical instrument devices to communicate to each other. MIDI has been around since the early 1980’s. It was primarily used with synthesizers and sequencers, but quickly got implemented on all kinds of musically-related gear (drum machines, mixers, drum pads, synchronization boxes, etc.)
As much as the jamstik has changed how people learn how to play guitar or record their ideas in GarageBand or other recording apps, it’s also a great controller for live performances. As someone who has spent years in guitar-based live bands with no keyboard players, trust me when I say it’s hard to cover three hours of familiar material for an audience in one night without running into a tune that needs a signature keyboard part.