>Happiness
 With the obvious punishment of rebellion from low happiness, a nation with high happiness can gain population/items from travelers from other nations and other bonuses.

>Food
Actions to "Harvest" gain food stacks. The # of food stacks gained are determined by the level of your food production and population size.
Food stacks are needed for population growth and military movement.
[Free Action: Eating ONE food stack per turn.]
The amount of food stacks a military unit needs depends on the travel distance, types of units, and size.

>Economy
Economy gives bonuses.
You can use economy to trade, buy from merchants, or whatever.
[Free Action: Can sell X amount of items to merchants per turn]
X is the combined levels of your [Market] and the [Trading Docks].