Tokøta from Mastering.com breaks down the two MIDI concepts that actually matter for playing and programming notes: note-on/off and velocity.
Note-on/off messages carry pitch values from 0 to 127, the full range MIDI uses regardless of instrument.
Velocity determines how soft or loud a note is perceived, but it's set by how fast you press the key, not how hard you hit it. Slow presses read low, fast presses push toward 127.
A quick, foundational grounding in Logic that applies to any MIDI controller or keyboard you play into a DAW.