Chalcedonian Christianity is a type of Christianity that believes in one God who is made up of three parts: the Father, the Son (Jesus Christ), and the Holy Spirit. They also believe that Jesus is both fully God and fully human at the same time. This is a bit like how a person can be both a child and a student at the same time.
This belief was developed in the 5th century in a meeting called the Council of Chalcedon. The people at this meeting wanted to figure out how Jesus could be both human and divine without being one or the other completely. They decided that Jesus had two natures, or ways of being: a divine nature as the Son of God and a human nature as an actual human being like you and me.
Chalcedonian Christians believe that this helps explain why Jesus was able to do amazing things like healing people and walking on water, but also experience human emotions like sadness and joy. They also believe that Jesus died on the cross and rose from the dead, which is an important part of their faith.
Overall, Chalcedonian Christianity emphasizes the idea that Jesus is both fully divine and fully human, and that this is an important part of understanding the nature of God and how He interacts with the world.