Action Points

Action Points are a kind of currency that the player must spend in order to take certain actions in a given turn. The player earns 12 new Action Points every turn, but only 4 unused Action Points carry over to the next turn.

Codex
"Each character has a set of Action Points per turn, which represents the amount of time they have to focus on different activities. Actions typically cost a number of Action Points to trigger, and you can no longer effectively act when you run out of Action Points.

Each character gets 12 action points at the beginning of their turn. There are also a set of standard bonuses and penalties that are applied to this number: - Happiness. A character that ended the previous tick happy will get a bonus to their action points, and vice versa. - Vassal Limit. The head of a house that has too many vassals has a penalty to their action points (relative to how overburdened their house is). - A character can transfer up to 4 unused action points to the next turn.

Important Note: Do not feel that you must spend your action points each turn. Action points act as a limit to how much a character can do in a single turn, but there will be many turns when there isn't something you can meaningfully do to improve your house's position. Lie in wait, and pounce when an opportunity arises."