After the death of the heirless King Charles, you engage in a struggle with other nobles to gain the crown of France.
A real-time strategy, but without all the buildings and troops. You can conquer provinces, build armies, gather resources, send out spies and diplomats, etc. It's a large historical event played on a much smaller scale.
The overland mode shows a map of France along with the territories you own or have explored. The in-battle mode is quite simple yet leaves some room for strategical maneuver. There is also a castle-building mode which allows you to design your own castle! Last but certainly not least, you can turn on Story Mode if you like. This opens many possibilities for you. Random mini-quests come by you.