All of these resources except gold are produced by buildings in your Fields. Farms are the most important for the upkeep of your city. Resource production can be increased by: building more field plots, conquering Wilds, appointing a hero to the production position, Completing appropriate Research, and using Items that boost production. All resources except Gold can be protected by your Vault. The higher your Vault's level, the more resources it can protect. Gold is produced by taxing your Population. You can adjust your tax rate in your Keep. Building and upgrading Homes can increase tax revenue by raising Population.
Resources can be transferred between your own cities or sent to Alliance members. As you progress you may look elsewhere for resources such as enemy cities. These enemy cities that you attack for resources are called farms.