What were the key theological differences between John Calvin and Martin Luther?

John Calvin and Martin Luther had key theological differences in their beliefs about predestination and the sacraments. Calvin emphasized the idea of predestination, or the belief that God has already chosen who will be saved, while Luther focused more on the idea of justification by faith alone. Additionally, Calvin believed in a more symbolic interpretation of the sacraments, while Luther believed in the real presence of Christ in the Eucharist.