Thus doth quoteth Gamasutra:

Robot Entertainment and Microsoft Game Studios have announced that the upcoming Age of Empires Online will adopt a slew of social features and persistent systems, as well as a free-to-play business model.

The game share  many real-time strategy elements seen in previous Age of Empires titles, and borrows elements from MMORPGs, allowing players to earn experience and gear via quests or crafting systems.

Unlike previous Age of Empires titles, the game encourages players to focus on developing their civilization over time, with cities that persist and earn resources even while the game is not actively being played.

Find out more about Age of Empires Online on the official site.