The next time the Great Schism comes up in conversation (which I’m sure is frequently), remember that the Great Schism of the Catholic religion, also called the East–West Schism, happened in 1054 and was the break between what are now the Roman Catholic and Eastern Orthodox churches. The Roman Catholic church was based in Rome, and the Eastern Orthodox in Constantinople, known as “new Rome”.
There are an abundance of political, cultural and theological reasons for the split, going back to the early days of the church, but a significant factor was a disagreement over the extent of the power that Rome and the Pope had over the Eastern churches.
The history of course is very complicated, but a big conversational takeaway is that although it wasn’t the first schism, it was the final one.
Enough said.