This Saturday is the inaugural Global Coptic Day, a day memorates the Holy Family’s flight to Egypt and that celebrates “the Coptic Orthodox Church’s rich heritage, including its indelible history of martyrdom and persecution, theological education and monasticism.” Here are five facts you should know about this ancient Christian tradition.

1.The word Copt is derived from the Greek word for Egyptian. After the Muslim conquest of Egypt, it became restricted to those Egyptians adhering to Christianity. The term is typically used in reference to members of the Coptic Orthodox Church, though it is sometimes used to refer to any Christian groups in Egypt.

2. Approximately 12 percent of the Egyptian population—roughly 11 million people—identify as Christian. Egypt’s Copts are considered the munity of Christians in the Middle East, which makes them a frequent target of Islamic terrorist groups. Outside of the region, there are about one million members of the Coptic Orthodox Church, mostly in Australia, Europe, and North America. About300,000 Copts live in the U.S., with the largest concentrations in New York, New Jersey, Boston, Chicago, Cleveland, Detroit, Houston, and Los Angeles.

3. According to tradition, the Coptic Orthodox Church was established circa AD 49 in Alexandria by St. Mark the Evangelist (the author of the Gospel of Mark), during the reign of the Roman emperor Claudius. In his fourth century bookEcclesiastical History, Eusebius writes, “And they say that this Mark was the first that was sent to Egypt, and that he proclaimed the Gospel which he had written, and first established churches in Alexandria.” (Ecclesiastical History2.16)

4. The first ecumenical council, the First Council of Nicaea (325), was convened in part as a result of a theological dispute over the nature of Christ that was begun by Arius, an Alexandrian presbyter. And in the fourth ecumenical council, Council of Chalcedon (451), the Copts separated from the other churches—a split almost 600 years before the East/West Schism of AD 1054.

5. Since their split with other Christian churches in the fourth century, the Coptic Orthodox Church has frequently been under persecution. When the Persians invaded Egypt in the sixth century, theydestroyed most of the churches and monasteries. The Persians were later replaced by Arabs, who made Islam the dominant religion in Egypt. As historianRobert Morgan says, “Until the present day in the twenty-first century, the Christian Copts of Egypt are still suffering great injustice and undeclared persecution under the Muslim yoke inside Egypt.”