Resources

§ The world of Civilization IV contain various "natural resources" that have benefits for the civilizations which possess them. Some provide military benefits - the "horse" resource allows the creation of mounted units such as the Chariot early on and Cavalry in the Renaissance period. Some provide productivity benefits - marble decreases the labor required to construct the Parthenon wonder, for example. Other resources provide health and happiness to your cities, allowing them to grow to larger sizes and increase in power. A civilization that possesses a variety of resources will have a distinct advantage over one that possesses few or no resources, and resources are one of the most important factors to keep in mind when choosing city sites with settlers.
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Discovering Resources

§ Some resources - rice, gold, etc. - begin the game visible. You will be able to see these resources as soon as their space is visible (see Exploration). Other resources are hidden at the start of play: they are not uncovered until you have acquired specific Technologies. Copper is a good example of such a hidden resource; at game start no copper is visible anywhere on the map, but once you acquire the Bronze Working technology, copper is revealed.
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Resource Locations

§ Resources must be within your civilization's Cultural Borders in order to be connected to your City Network.
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Working Resources

§ In addition to resources' special abilities, they also usually provide some kind of food, commerce, or production bonus to their space. For example, a wheat resource adds a significant amount of food to the tile on which it is located. If a resource space is within a city radius, that city's laborers can work that space like any other - and they will almost certainly want to, since resources are usually highly desirable tiles.
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Resources and Improvements

§ Resources require that "improvements" be made to their spaces before you can access their special bonuses (see Improvements for more details). Improvements are constructed by Workers (except for water resources, which are improved by Work Boats). If an improvement is pillaged or otherwise destroyed, you lose the resource's benefits until the improvement is reconstructed.
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Duplicate Resources

§ It is quite possible to have two or more of the same resource within your borders. Except for each space's production, commerce, and food value (see "Working Resources" above), you gain no additional benefit from multiple resources; a single resource is enough to take care of all of your civilization's needs. You may wish to hold onto the extras in case one is captured by an enemy, or you may want to trade the extras to other civilizations in exchange for their extra resources (see below).
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Trading Resources

§ You can trade any resource to other civilizations if that resource has been improved, and if it is connected by your City Network to your capital city (see Diplomacy for more details on trading).