Transubstantiation is the belief of Catholics and some other Christian churches that the bread and wine that are eaten and drunk at Mass becomes (changes into) the body and blood of Jesus, who Christians believe is the son of God.
Beliefs about transubstantiation
Christians who believe in transubstantiation believe that the bread they eat at Mass is the body of Jesus. They know that the bread still tastes like bread, looks like bread and smells like bread. It is just like bread, but it becomes the body of Jesus. The priest says prayers at Mass so that the bread and wine become the flesh and blood of Jesus.
This started when Jesus ate a meal called the Last Supper the night before he died. He said that the food his friends were eating was his body and blood. In the Gospel of Matthew 26:26, it says, "Take this [bread] all of you and eat it. This is my body which will be given up for you," which means that he would die for them. Then, in Matthew 26:27, Jesus said, "Take this [cup] all of you and drink from it. This is the cup of my blood, the blood of the new and everlasting covenant." This means that Jesus's blood would make a promise forever between God and his people. Then he said, "My blood will be shed for you and for all so that sins may be forgiven." This means that Jesus would die for everyone so their sins, or things they do wrong, could be forgiven. Then he said, "Do this in memory of me." This is Jesus commanding people to continue what he did. From that time until now, people have continued what Jesus did and it reminds them of the Last Supper.
The Last Supper (upper image) and preparatory washing of feet (lower image) in a 1220 manuscript in the Badische Landesbibliothek
The Disputation of the Holy Sacrament (Raphael 1509-1510) depicts theologians debating Transubstantiation, including four Doctors of the Church, with Pope Gregory I and Jerome seated to the left of the altar and Augustine and Ambrose to the right, Pope Julius II, Pope Sixtus IV, Savonarola and Dante Alighieri.
Title page of Martin Luther's De Captivitate Babylonica Ecclesiae
Transubstantiation Facts for Kids. Kiddle Encyclopedia.