Imagine that you and your best friend have a really big argument about who should be the leader of your club. Your friend thinks that they should be the leader and have all the power, but you think that everyone should work together and make decisions as a group. This argument is kind of like the one that the Eastern Orthodox Church had with the Catholic Church a long time ago.
The Eastern Orthodox Church is a religious group that has followers in many different countries, such as Greece, Russia, and Romania. They have different beliefs and practices than the Catholic Church, but they both believed in God and Jesus. However, one big difference between the two was that the Catholic Church had a Pope who was seen as the ultimate leader and had the power to make decisions for all the Catholics in the world.
The Eastern Orthodox Church did not believe that the Pope should have all this power. They thought that each bishop (a leader of a local church) should have more say in how the church was run, and that decisions should be made among all the bishops, rather than just by one person. They saw the Pope as just another bishop, not as someone who should have authority over everyone else.
This difference in opinion caused a lot of tension between the two churches, and eventually led to them splitting apart. Today, we still have both the Catholic Church and the Eastern Orthodox Church, but they remain separate and have their own beliefs and practices.