OK, I know the following is just Wikipedia, but it's not as if I ever claimed to be a scholar or anything. While not a scholarly source, what this article says is pretty much what I have always heard:
Egypt is identified in the Bible as the place of refuge that the Holy Family sought in its flight from Judea: "When he arose, he took the young Child and His mother by night and departed for Egypt, and was there until the death of Herod the Great, that it might be fulfilled which was spoken by the Lord through the prophet, saying, Out of Egypt I called My Son" (Matthew 2:12-23).
The Egyptian Church, which is now more than nineteen centuries old, regards itself as the subject of many prophecies in the Old Testament. Isaiah the prophet, in Chapter 19, Verse 19 says "In that day there will be an altar to the LORD in the midst of the land of Egypt, and a pillar to the LORD at its border."
The first Christians in Egypt were common people who spoke Egyptian Coptic , there were also Alexandrian Jews such as Theophilus, whom Saint Luke the Evangelist addresses in the introductory chapter of his gospel. When the church was founded by Saint Mark during the reign of the Roman emperor Nero, a great multitude of native Egyptians (as opposed to Greeks or Jews) embraced the Christian faith.
Christianity spread throughout Egypt within half a century of Saint Mark's arrival in Alexandria as is clear from the New Testament writings found in Bahnasa, in Middle Egypt, which date around the year AD 200, and a fragment of the Gospel of John, written in Coptic, which was found in Upper Egypt and can be dated to the first half of the second century. In the second century, Christianity began to spread to the rural areas, and scriptures were translated into the local language, namely Coptic.
Contributions to Christianity
The Catechetical School of Alexandria
The Catechetical School of Alexandria is the oldest catechetical school in the world. St. Jerome records that the Christian School of Alexandria was founded by St. Mark himself. Around AD 190 under the leadership of the scholar Pantanaeus, the school of Alexandria became an important institution of religious learning, where students were taught by scholars such as Athenagoras, Clement, Didymus, and the native Egyptian Origen, who was considered the father of theology and who was also active in the field of commentary and comparative Biblical studies. Origen wrote over 6,000 commentaries of the Bible in addition to his famous Hexapla.
Many scholars such as Jerome visited the school of Alexandria to exchange ideas and to communicate directly with its scholars. The scope of this school was not limited to theological subjects; science, mathematics and humanities were also taught there. The question-and-answer method of commentary began there, and fifteen centuries before Braille, wood-carving techniques were in use there by blind scholars to read and write.http://en.wikipedia.org/wiki/Coptic_Orthodox_Church_of_Alexandria#Apostolic_foundation