How is Charm used and what increases it?

[Kethus]

I think it's used when determining success chances in conversation options because that makes the most sense. It apparently increases wit bartering, but offering denars to looters doesn't count. The only other occasion that brings up the barter screen is when I ask a lord to trade, but they only ever have horses to offer. It should increase on improving relations with people, but doesn't count when I do it via quests and gifting them money doesn't improve their oppinion on you. Is Charm some late-game skill that I don't get? I thought I could use it to resolve quests without conflict.

 

[Jonlit]

Charm is very very important later if you want to recruit vassals to join your kingdom.
I assume it will have plenty more uses later on when they've added more features though.

Increase charm by letting lords go free after defeating them in battle.
Might me more ways but this is the one I leveled up my charm in.

Works well too because the clans I release after battle also become good friends even though I just slaughtered their entire army and are much more inclined in joining my kingdom later on.