Create a MIDI File (*.mid)
Use File: Export to save the current work as a MIDI Type 0 or Type 1 MIDI file. The choice is based on your selection from the Save as type box.
Type 0 MIDI files are always one track with one or more channels. Type 1 MIDI files can be one or more track.
As far as which type to use, this question is better answered for the receiving software. However, select Type 1 if the receiving software will accept it (most do).