In fact the only thing that uses resources is whatever yous end the MIDI to in order to make sound, typically a software instrument.
It’s weightless too, meaning that MIDI data uses virtually no space and no CPU power. MIDI can be copied, pasted, altered, manipulated and re-routed easily. The great thing about basing a lot of your composition on MIDI tracks is that they are almost endlessy flexible, with none of the limitations of digital audio files.