Calvinism is a Protestant theological system that John Calvin and those that followed him, it follows Luther’s doctrine of justification by faith alone into an emphasis on the grace of God and centres on the doctrine of predestination.
Predestination in Christian theology is the doctrine that God has ordained all that will happen, especially with regard to the salvation of some and not others.
It has been particularly associated with the teachings of St Augustine of Hippo and of Calvin.
We are the pure and the chosen few, and all the rest are damned. There’s room enough in Hell for you — we don’t want heaven crammed.