Here's a partial explanation that occurred to me, perhaps it may be of some value.

Say you have a really nice acoustic guitar thing you just improvised (on a real guitar!) and recorded, recording in two forms: audio and MIDI.

The audio recording captured however you sounded when you recorded it, on whatever real guitar you played. You can add post-production effects, reverb and such, but the underlying audio is fixed. It's what you played on that guitar.

The MIDI recording, on the other hand, can be rendered in production however you please, as a guitar or piano or violin or saxophone orchestra or 1950s electronic sounds or maybe a flock of sampled geese.

Consider how you might use those two recordings as material to slice and dice and recombine, for use in different creative projects going forward.