The MIDI port you want to receive MIDI messages from. This is used for live input from MIDI devices connected to your computer.
MIDI Thru
Whether to send MIDI messages from the MIDI Input to the MIDI Output. This is useful when you want to use the same VST for both playback and live input.
MIDI Output
MIDI Input
The MIDI port you want to send MIDI messages to. This port is typically connected to a VST host.