YS compares it to the split between Alertness and Investigation with respect to the Presence trapping "Charisma." As it says, "As a rule of thumb, the GM may ask you to roll Presence to gauge impressions when you are not actively focusing your efforts on making one. Further, when you use Rapport to make a deliberate impression, you can call in Presence to complement the skill." Presence is used passively. You enter a social situation, and your Presence passively affects the people therein, like when you walk down a hall and Alertness triggers on its own (because of ninjas or something.) Presence is also your Reputation and Social Stress Track, so it's a big part of Social Fortitude. A tanky socialite needs a high presence to be able to resist their foes in Social combat. The Command trapping is also a big deal for teamwork stuff, like coordinating a big maneuver or something cool. Looking at the RAW vol.1, Rapport's trappings are pretty much just brass tacks actions for someone who has already initiated a Social Conflict, and not much else (except the Chit-Chat trapping, which is some aces stuff.)
