Cities consist of a central district surrounded by exploitations, all of which provide their terrain's basic resources. Citizens may be assigned as workers to produce resources of any desired type; a variety of buildings and other factors can increase the number of resources produced per worker.
Cities may expand to adjacent hexes in order to spread their range of resource capture, but may not expand past the region's borders. Only one city may inhabit a region at a time.
There are several types of resources in Auriga, and different terrain will produce a different mixture of yields.
Food is used to maintain and expand your population. Population is calculated independently per city.
Industry is used to manufacture units and structures.
Dust is used to maintain armies and structures, as well as to buy items immediately rather than manufacturing them with Industry.
Science is used to research technologies.
Influence is used for a variety of diplomatic and social purposes, but generally serves to strengthen your empire and interact with entities that are not your empire.
Some terrain is relatively uninteresting, and produces fairly basic yields.
Other tiles contain interesting and usually profitable anomalies.
Finally, some tiles contain strategic or luxury resources. In addition to sometimes increasing standard resource yields, strategic and luxury resources are harvested as separate resources. Strategic resources are used to construct some buildings and in advanced weapons and armors. Luxury resources are activated to give an empire-wide boost for a number of turns; typically, this boost will consist of an approval increase and another resource-specific benefit.
Unlike basic resources, harvesting strategic and luxury resources require a specialized extractor to be researched and then built on top of them. City districts may also fill in for extractors here, allowing you to expand cities over valuable resources without concern.
While expensive, it is also possible to acquire strategic or luxury resources from the luxury marketplace, once the appropriate technology has been researched. Doing so requires Dust, and the cost goes up the more is purchased.