Midi is just note on/note off data. When you record a midi track you aren't recording the audio. You are recording a series of binary notes, and you have to assign those binary notes to trigger the sounds you want.

You can do this by using soft synths that reside within your DAW program, or, you can trigger external synths/keyboards/tone modules. To get that information to reside in an audio form, you would have to render internal soft synths to an audio track, or, you could come out of the audio outputs of external synths to the input of your audio I/O, and bus it to an audio track in your DAW program, just like you would record any other sound source ( vocals, guitars, etc)

Any changes you make along the way while recording the midi - note on, note off, sustain, velocity, duration, mod wheel, pitch wheel, patch change, etc., will all be recorded as such on the midi track. You simply need to tell that midi track what to do with that information once you have recorded it.

If you want to use the sounds of an external synthesizer, you would need to come out of your midi port (midi out) on your computer, to the midi in port of your external synth.
This will trigger your external synth to play (as long as your external synth is correctly set up to receive midi data). To get the audio from that synth back to you DAW in audio form, you would come out of your synth's audio outs, to the audio inputs of your audio I/O device, and assign that audio to an audio track in your DAW.

To use internal synth sounds (soft synths, vsti's) you would record the midi data to a midi track, and then assign that midi track to trigger an internal synth program. Most DAWS will allow you to take that midi track, along with the audio output of the soft synth track, and render it to an audio track. Depending on the program you use,.. sometimes it's referred to as "Bounce to tracks", or "Render To Tracks". You would know best what your DAW's program's command is in this regard. Check your manual to see how your particular program handles this function.

With some DAW's and soft synth layouts, you would insert a soft synth into your project, at which point the soft synth creates both a midi track and an audio track for that soft synth. The audio track it creates isn't necessarily an audio track that you would use to edit audio with..it's simply an audio output. If you want to be able to edit audio in the purest form, you would need to create an additional audio track, and then, selecting the midi track and it's audio output track, highlighting them both, you would render those to a dedicated audio track. Again, check your documentation to see how your program handles this function.

FWIW
-d.