In Age of Empires, the Wheel is a technology that can only be researched at the market once the player reaches the Bronze Age. Once researched, the working speed and movement of all villagers increases by 33%. It is a very useful upgrade as the benefits from this greatly offsets the cost of this technology. This technology must be researched in order to train chariots and chariot archers.
Almost all civilizations can research this upgrade. The only exception to this are the Persians and the Macedonians. To research this economic upgrade, 175 Food and 75 Wood is required.