The Byzantine Empire made many contributions including preserving Greek and Roman cultures. The empire was responsible for ensuring that the words of many great philosophers survived.
Even though the world began falling to major western influences, Byzantine scholars continued to protect and study the works of Plato and other Greek philosophers in order to pass down the teachings. This also allowed the empire to bring their studies to countries such as France and England which in turn, helped spark the Renaissance Era. This era laid the main foundations for technological and scientific advances in the modern world.
Even after the Byzantine Empire fell to the Ottoman Empire in the mid 1450s, the legacy and influences of the Byzantines continued to influence many parts of the world. One instance of this is when great Italian Renaissance scholars relied heavily on the Byzantine scholars to help them translate the texts of ancient pagans and Christians.
During its reign, the empire also helped protect Europe from destruction, both in the cultural and military sense. The Byzantine Empire was powerful and rich, so much in fact, it closely rivaled the Roman Empire. This allowed them to protect themselves and neighboring empires from invasion and military defeats.