Description taken from PC version of this game

Following a well-received break to the realms of ancient mythology, Ensemble Studios returns its real-time strategy sensibilities to the real world with this third edition of the historically themed Age of Empires series. After conquering the Continent in earlier editions and expansion packs, the series stakes claim to the New World in Age of Empires III. Players choose to guide one of eight Old World powers, and manage their empire from a European home city, but all of the base-building, battle, and conquest take place across the sprawling untamed wilderness of the Americas. Each home county is offers different advantages, such as Britain's economic strength, France's propensity for allegiance with Native American civilizations, or Spain's formidable colonial presence.

Although Age of Empires III offers the sophisticated style of real-time strategy established earlier in the franchise, some aspects have been streamlined and others deepened. While settlers are still required to collect resources, they no long need to carry them back to a drop-off point. Players still race to advance from one technological "Age" to the next, but with each jump they may gain new political or diplomatic abilities, as well as technological proficiencies. Victory on the battlefield still relies on balanced forces and good tactics, but it now also rewards the player's home city with influential experience that adds to the empire's overall power. ~ T.J. Deci, All Game Guide