Culture helps you to ensure your population is healthy and productive. You will mainly need culture to upgrade buildings (together with Population and other resources). The higher the level of a building, the more Culture Points it will require. You can get Culture mainly from Cultural Buildings, but also from advanced street types.
If you have more Culture than your upgraded buildings are currently using (the “Required Culture”), the remaining “Available Culture” will give you a Culture Bonus, which will increase your base resources productions of Coins and Supplies. You can get temporary additional “Available Culture” from Neighborly Help. This will help you to get to the higher levels of Culture Bonus.
There are 4 levels of culture bonuses:
Level 1 will increase your production rate from the standard 100 % to 120 %. You should definitely try to get this.
Level 2 will increase it from 120 % to 140 % and is not easy to achieve.
Level 3 will increase it from 140 % to 170 %, but you will rarely reach it without neighborly help.
Level 4 will increase it from 170 % to 200 %, only a steady flow of neighborly help will ensure you can get this bonus without having to occupy too much space for culture buildings.
With Cultural Buildings you will make your city more beautiful and you will increase your available Culture. After unlocking a Cultural Building in the Research Menu, you will be able to build it via Build menu.
You need to unlock Cultural Buildings in the Research Menu. They can be moved, sold and rebuilt. They cannot be upgraded.
Sell Cultural Buildings: Over time, you will research newer Cultural Buildings which give more Culture. Often it is recommendable to exchange your older Cultural Buildings with the newer ones to save space in your city.