More experience bubbles, new moves, stats and so on, yeah.
For instance, "Banners of War" will add a character sheet for the mercenary company you lead. It'll have experience bubbles for things like "we won a battle," "we lost a battle," "we seized and occupied a prince[ss]'s palace," "we were routed and scattered," and so on. It'll have stats for your company and moves for recruiting warriors, finding battles to fight, and negotiating their outcomes.
You can think of them as leveling up.
-Vincent