voice leading
How each line moves note-to-note from one chord to the next.
The craft of moving each voice smoothly from one chord to the next, ideally by small steps rather than leaps. Good voice leading is why a progression sounds like several independent lines rather than a stack of blocks, and it is the whole concern of counterpoint. The engine watches it for you: parallel fifths and octaves are voice-leading faults.
Learn it: Counterpoint · Voices
The one-sentence definition at the top is the same one the Theory Aide extension shows as a tooltip inside Ableton Live. Hover any dotted term for its own.