1. Territory, You can take the enemies territory (1) after a war is finished. If the war was siege battles, you take a fort, if it was fields, you take a village, if it was in their capitol, you take the leader hostage and put him in one of your forts.
2. Prisoners, By winning the battle, you can take the enemy general "prisoner" and place him in one of your forts. He cannot join battles until that fort is taken.
3. Money, By winning, you can take the enemies money, wether it's all or 1 silver coin. Money will be a major rescource later on.