I understand tracking relates to all pairs and word spaces while kerning relates to specific pairs. I’m wondering about how tracking is related to kerning: Is tracking added to kerning linearly, across all pairs equally, or is it more like a scaling factor for individual kerning distances?
Kerning is the defined space between two characters. All pairs of characters have kerning (either default kerning, defined kerning for the pair in the font, or kerning calculated by the DTP software).
Tracking would add (or remove) from the space that's already defined from kerning.