Pope Benedict XVI is the head of the Holy See of St. Peter, while Shenouda III was the head of the Holy See of St. Mark... confused yet? Just wait...
The Coptic Church has existed roughly since the 5th century when it split from the Roman Catholic Church; the split essentially has to do with the nature of Christ - Catholics believe that Christ had two natures, Human and Divine, while Copts believe only in the Divine nature of Christ.
Shenouda III was the 117th Patriarch of Alexandria (his other title) and there are about 16 million Coptic Christians world wide-12 million of which live in Egypt; the location of the Holy See of St. Mark.
Shenouda was known to be an advocate of Christian-Muslim relations and a strong believer that the two religions could coexist in peace. He himself had been exiled in the desert monastery of St. Bishoy in 1982 by the then President of Egypt Anwar Sadat; Sadat stripped him of his powers for criticizing Islamic extremists. Shenouda was freed by President Mubarak, who was ousted from power during last year's "Arab Spring Revolutions."
Sehnouda will be buried at St. Bishoy; his body will be transported there from Cairo by a military transport.... there is no set timetable for picking his successor.