From the back of the box and inside the rulebook:
INFLUENCE is a tactical card game where players attempt to gain the most Power by playing Influence cards – symbolizing military, political, and economic influence – to conquer Castles. Conquering and maintaining control of these Castles builds Power, as well as granting Influence over neighboring Castles!!
Each player has an identical set of Faction cards. With these, players will leverage Influence over Castles, alter the game board, and sabotage opponents’ strongholds. At the end of six Rounds, whoever has the most Power wins!