At first, the Byzantines were simply Romans. Over time, the Roman Empire became too big to control. The western lands grew poorer and weaker, while the eastern lands became richer and more powerful because of trade. This was because they were closer to Asia and Africa which produced many great and exotic trade goods.
A Roman emperor named Diocletian decided the empire was too large for one ruler. He split it into two parts—the Western Roman Empire and the Eastern Roman Empire. This helped make ruling easier.
In the west, Rome eventually collapsed. But in the east, the empire lived on. This eastern empire became known as the Byzantine Empire, with its capital at Constantinople, one of the greatest cities in the world.