MIDI, Musical Instrument Digital Interface, is a system specifying the connections and communication protocols for synthesizers, digital instruments, computers, and other devices.
A MIDI channel is the routing of MIDI data for one musical instrument or synthesizer. A MIDI cable can contain up to 16 channels.
A MIDI controller is a device (such as a keyboard or drum pads) played by a musician that outputs MIDI data.
A MIDI interface converts MIDI data into a digital format that can be used by a computer and converts digital data into a MIDI signal.