SwadianJedi said:
Recently, ISIS executed 21 Egyptian Copts. This lead me to the question what is Coptic Christianity, and what makes it different from other sects of Christianity? I tried to google it, but all the answers were long and filled with incomprehensible religious terminology.
Well, apart from incomprehensible religious terminology they are very similar to the Greek Orthodox - top-down hierarchical organization, the priests wear beards, can get married and they have monasteries with monks.
In terms of religious stuff, Christianity in Egypt evolved in before its adoption by the Roman powers that be and though the Coptic Church traces its origin back to apostle Mark, this is about as historical as Catholic Popes having an uninterrupted line of popes going back to apostle Peter.
As Christianity grew in numbers in the first three centuries there were some differences that were just bound to spring up in a community that big. This surfaced most intensely right after the establishment of the universal church at the councils of Nicaea and Constantinople and is usually known as the Christological controversies, which is a fancy word for "who exactly was Jesus?"
The first casualties were the Arians who essentially claimed Jesus was some uberhuman, or ultraprophet. A very important dude, but in the end just a man whom God chose. They lost so thoroughly there aren't any actual Arians anymore, but they were quite popular in their heyday.
Then in come the Nestorians who say that Jesus was both human and divine, but these two "essences" are somehow separate in his personality. What the **** is that supposed to mean, no one knows, but anyway they were promptly declared anathema and expelled from the universal church at the council of Ephesos in 431. They didn't give much **** and continued to go on about their business, mostly in the easternmost provinces of the Empire and even further east - Persia and India. There are still some out there (e.g. Assyrian Church of the East) but most of them later converted to Islam etc or joined the Catholic church in the early modern era.
Then as a sort of reactionary opposition to the Nestorians come the Monophysites* who claimed that Jesus was both human and divine and these two essences were thoroughly mixed resulting in one awesome Jesus. This was a for a while considered the Orthodox position, but it too was eventually declared anathema at the Council of Chalcedon. So again there was a split, the Monophysites eventually prevailed in Egypt, Ethiopia and Armenia, which is why these countries have separate churches and which is exactly what the Coptic Church is.
The rest of the Empire went with yet another definition of Jesus and 600 years later split into Catholics and Orthodox over a different, but equally as ridiculous theological issue.
*- for more confusion, the Monophysites consider the term an insult, prefering to call them Miaphysite claiming their actual position is pretty similar if not identical to Catholic/Orthodox.