Civilization – Who performed the works of John Adams for the Civilization 4 soundtrack

White circles denote fields on which the population of a city are working, thus generating food/production/trade (coins) resulting from given squares. You can rearrange the population to suit your needs, so if you would prefer more food or extra trade (coins), you can deactivate worker from active (white circle) field and assign him of her to another.

Each non-capital city starts with culture 0, thus only has access to 9 adjacent tiles. After reaching first level of culture (10 points), its borders expand and it gets full access to all tiles that are max. 2 non-diagonal squares away from the city centre. Note that every city always automatically generates resources from square composing the city centre, without assigning any population there (unless riots occur in the city).

Food determines how fast your city grows, at the top of the city screen is a bar that shows how much food is stored. When that bar is full the city grows one population point and the bar is emptied again.

Each population point of your city eats some food, that is subtracted from the total food earned and only the excess food goes towards growing your city.

Each population point means you can work one tile more of the city, that is a considerable bonus. As long as your city is happy, additional population is very helpful. You should try to keep your population below the limit where they are getting unhappy.