Entering a new Age enables you to own more armies or units, structures, and technologies but it also places you in a major historical event. You will progress through each age chronologically by gathering your resources, creating towns, and building armies that can topple rival empires.
Age of Empires II: The Age of Kings is a real-time strategy video game that is set in the Middle Ages, specifically the Dark Age, the Feudal Age, the High Middle Ages, and the Renaissance.