Resources are the basic building blocks you'll need to expand and sustain your empire. They are acquired primarily from cities.
Empire Resources[]
These resources are tracked for your empire as a whole; no matter where you got them, they all go into a central pool and can be spent wherever they are needed.
Food[]
Food is generated by farmers. Every turn, each unit of your population will consume 1 food. If you don't have enough food for everyone in your empire, your growth rate will be reduced. Excess food will be saved for future use.
Minerals[]
Minerals are generated by miners, and are consumed by production on a one-for-one basis. If you don't have enough minerals, your production will be reduced. Excess minerals will be saved for future use.
Science[]
Science is generated by scientists, and is used to research technology. You must choose a particular technology to research; all your science will be applied toward that technology until it is finished or you choose a different technology.
If you finish a technology, any excess science will carry over into your next turn, and then be applied to the next technology you select (it is not possible to complete more than one technology each turn). If you change your research plan before finishing your current technology, the science you've accumulated stays with the old technology; you will have to start the new one from scratch, but you will still have all your progress on the old technology when you switch back to it.
Credits[]
Credits are generated by all population based on the tax rate. Credits are needed to pay maintenance on your buildings and units; if you don't have enough credits, your buildings may be sold and your units may desert you. Credits can also be used to rush construction, to refit your units with new equipment, and as enticements in diplomatic deals with other factions. Excess credits will be saved for future use.
City Resources[]
These resources are tracked separately for each of your cities, and they apply only within that city; they cannot be moved around freely.
Production[]
Production is generated by workers, and is used to construct a variety of useful things in cities. Every point of production consumes 1 mineral.
Growth and Population[]
Growth accumulates in a city until it reaches a certain threshold, at which point it increases the city's population. A higher population means you have one more person that can be assigned to any role in the city, and also increases the credits earned from taxes and adds to the city's growth, generally increasing the overall productivity of your empire; however, each unit of population also consumes food every turn, occupies habitat space, and generates pollution.
Although growth is tracked separately for each city, it acts much like an empire-wide resource, because the amount of growth required to add 1 population is based on the combined population of all your cities, and population can move between your cities through migration.