The MIDI settings page lets you enable and disable TouchViZ's MIDI capabilities globally and lists all available CoreMIDI inputs and outputs which can be enabled and disabled individually.
The Refresh button in the top right corner will cause the application to scan for available MIDI devices.
The Send Clip Positions settings lets you specify wether TouchViZ will send the positions of currently playing clips to all enabled MIDI outputs. This can cause a lot of MIDI messages to be sent and it is advised that you disable this feature if you do not need to display clip positions.
Please see the MIDI Reference for all MIDI messages that TouchViZ sends and receives.