Upon reuniting of the Roman empire by Constantine the Great, he looked for a place that could be truly a center for a new Roman Empire that was centered on the Christian faith. The reason that he chose the site of Byzantium was two fold. First, it was a logical link to the eastern parts of the empire and second it would provide a formidable defense to any aggression from the Persians in the east.
The transformation of the Roman empire into that of the Byzantine empire was slow and did not have any real dividers in time. The "Byzantines" really considered themselves "Romans" and it was not until the divisions that occurred between the papacy and the eastern orthodox church was there any differentiation between the two. Remember that the Ostrogothic and Visigothic conquests within the western hemisphere of the empire made many changes in values, disciplines and beliefs. The word "Byzantine" was not used until well in the 15th century to describe the eastern part of the Roman empire. However, there were many conflicts between the eastern and western parts of the empire, mostly due to religious differences and monetary jealousy.
The beginning of the "Byzantine Empire" was of course with the establishment of Constantinople in 330. Constantine the Great wanted this city to be built from scratch as the center of the Christian world. He and his following emperors made Constantinople into one of the most elaborate and civilized cities in the world. The wealth that was displayed was incredible. Until the Fourth Crusade, Constantinople enjoyed 874 years of growth and stability. Few cities in history have lasted as long without being overrun by an invading army.
The monetary history was probably the most important aspect of the success of the empire. Constantine the Great introduced several monetary reforms with one of them being the creation of the gold Solidus at 72 to the Roman pound. This standard lasted throughout the history with only periodic debasement in economically stressed parts of the empire or during periods of extremely weak leadership. If anything can be learned from the Eastern Roman Empire is that monetary stability and strength lead to strength within a civilization.
The Byzantine Empire emerged as part of the Roman Empire but became into its own after the fall of Rome in 476 C.E. Its capital and the cultural center was built by Roman Emperor Constantine and named Constantinople (modern-day Istanbul, Turkey). The empire was founded on Roman traditions with Greek and Persian influences.
The Byzantine Empire was a crossroad of trade and center of diversity. Using the Silk Road goods from China and India came through Constantinople and into Europe. Wealth from this trade, allowed the arts and learning to flourish within the empire at the same time Western Europe was floundering in the Dark Ages.