Gameplay:

Players begin with a constructed town center or a wagon that will build into such, an armed explorer, and a modest number of villagers. Players explore the map and begin gathering resources used to build additional units and buildings and to research upgrades or technologies. Actions such as training units, constructing buildings, killing enemy units, etc., earn the player experience points. At certain experience point thresholds, players earn shipments that may be turned in for cards from the player's Home City, which can include units, upgrades, or resources. The game progresses similarly to most real-time strategy games until one side resigns.
In Age of Empires III, the player advances through technological "Ages", representing historical time periods; these provide access to greater improvements, units, and buildings. They include the Discovery Age, which represents the discovery and exploration of the Americas by Europeans and allows the player to explore and develop their economy; the Colonial Age, which represents the European Expansion into the "New World" and unlocks early military units; the Fortress Age, which represents the fortification of the European colonies, unlocks forts, and allows the player to have a more complete military; the Industrial Age, which triggers a strong economy, due in part to factories—advanced buildings that automatically produce resources or artillery—and unlocks all units and shipments; and the Imperial Age, which unlocks all buildings and upgrades, and allows you to send unit and resource shipments a second time. All Ages cost food and coin to advance to, except the Colonial Age, which only costs food (800). The price of age advancement is incremental but does not vary between civilizations.